Serum levels of hydroxylated metabolites of arachidonic acid cross-sectionally and longitudinally predict knee pain progression: an observational cohort study

OBJECTIVE

To examine associations between serum oxylipins, which regulate tissue repair and pain signalling, and knee pain/radiographic osteoarthritis (OA) at baseline and knee pain at 3 year follow-up.

METHOD

Baseline, and 3 year follow-up, knee pain phenotypes were assessed from 154 participants in the Knee Pain in the Community (KPIC) cohort study. Serum and radiographic Kellgren and Lawrence (KL) and Nottingham line drawing atlas OA scores were collected at baseline. Oxylipin levels were quantified using liquid chromatography coupled with mass spectrometry. Associations were measured by linear regression and receiver operating characteristics (ROC).

RESULTS

Serum levels of 8,9-epoxyeicosatrienoic acid (EET) (β(95% confidence intervals (CI)) = 1.809 (-0.71 to 2.91)), 14,15-dihydroxyeicosatrienoic acid (DHET) (β(95%CI) = 0.827 (0.34-1.31)), and 12-hydroxyeicosatetraenoic acid (HETE) (β(95%CI) = 4.090 (1.92-6.26)) and anandamide (β(95%CI) = 3.060 (1.35-4.77)) were cross-sectionally associated with current self-reported knee pain scores (numerical rating scale (NRS) item 3, average pain). Serum levels of 9- (β(95%CI) = 0.467 (0.18-0.75)) and 15-HETE (β(95%CI) = 0.759 (0.29-1.22)), 14-hydroxydocosahexaenoic acid (β(95%CI) = 0.483(0.24-0.73)), and the ratio of 8,9-EET:DHET (β(95%CI) = 0.510(0.19-0.82)) were cross-sectionally associated with KL scores. Baseline serum concentrations of 8,9-EET (β(95%CI) = 2.166 (0.89-3.44)), 5,6-DHET (β(95%CI) = 152.179 (69.39-234.97)), and 5-HETE (β(95%CI) = 1.724 (0.677-2.77) showed positive longitudinal associations with follow-up knee pain scores (NRS item 3, average pain). Combined serum 8,9-EET and 5-HETE concentration showed the strongest longitudinal association (β(95%CI) = 1.156 (0.54-1.77) with pain scores at 3 years, and ROC curves distinguished between participants with no pain and high pain scores at follow-up (area under curve (95%CI) = 0.71 (0.61-0.82)).

CONCLUSIONS

Serum levels of a combination of hydroxylated metabolites of arachidonic acid may have prognostic utility for knee pain, providing a potential novel approach to identify people who are more likely to have debilitating pain in the future.

Influence of central aspects of pain on self-management in people with chronic low back pain

OBJECTIVE

This observational study investigated whether central aspects of pain are associated with self-management domains in individuals with chronic low back pain (CLBP) undertaking a pain management program.

METHODS

Individuals with CLBP provided pain sensitivity and self-management data at baseline (n = 97) and 3-months (n = 87). Pressure pain detection threshold (PPT) at the forearm, temporal summation (TS) and conditioned pain modulation (CPM), Widespread Pain Index (WPI), and a Central Aspects of Pain factor (CAPf) were considered as central aspects of pain. Self-management was measured using the 8 domains of the Health Education Impact Questionnaire, as well as Pain Self Efficacy and Health Care Utilisation questionnaires.

RESULTS

PPT, CPM, WPI and CAPf predicted worse performance in several self-management domains at 3-months (r = 0.21 to 0.54, p < 0.05 overall). In multivariable regression models (adjusted for baseline scores of self-management, depression, catastrophization, pain and fatigue) low PPT, high TS, and high CAPf at baseline predicted poorer self-management at 3 months (R2 =0.14 to 0.52, β = -0.37 to 0.35, p < 0.05).

CONCLUSIONS

Central aspects of pain are associated with impaired self-management, over and above effects of pain intensity, fatigue, depression and catastrophizing.

PRACTICE IMPLICATIONS

Treatments that target central aspects of pain might help improve self-management in people with CLBP.

The Difficulties of Managing Pain in People Living with Frailty: The Potential for Digital Phenotyping

Pain and frailty are closely linked. Chronic pain is a risk factor for frailty, and frailty is a risk factor for pain. People living with frailty also commonly have cognitive impairment, which can make assessment of pain and monitoring of pain management even more difficult. Pain may be sub-optimally treated in people living with frailty, people living with cognitive impairment and those with both these factors. Reasons for sub-optimal treatment in these groups are pharmacological (increased drug side effects, drug-drug interactions, polypharmacy), non-pharmacological (erroneous beliefs about pain, ageism, bidirectional communication challenges), logistical (difficulty in accessing primary care practitioners and unaffordable cost of drugs), and, particularly in cognitive impairment, related to communication difficulties. Thorough assessment and characterisation of pain, related sensations, and their functional, emotional, and behavioural consequences ("phenotyping") may help to enhance the assessment of pain, particularly in people with frailty and cognitive impairment, as this may help to identify who is most likely to respond to certain types of treatment. This paper discusses the potential role of "digital phenotyping" in the assessment and management of pain in people with frailty. Digital phenotyping is concerned with observable characteristics in digital form, such as those obtained from sensing-capable devices, and may provide novel and more informative data than existing clinical approaches regarding how pain manifests and how treatment strategies affect it. The processing of extensive digital and usual data may require powerful algorithms, but processing these data could lead to a better understanding of who is most likely to benefit from specific and targeted treatments.

The association of painful and non-painful morbidities with frailty: a cross sectional analysis of a cohort of community dwelling older people in England

INTRODUCTION

The association between chronic pain and frailty might indicate that pain is an independent driver of frailty but might alternatively be explained by inclusion within frailty identification tools of morbidities that commonly lead to chronic pain. This research examines the extent to which the association of pain with frailty might be attributed to morbidities.

METHODS

A cross-sectional analysis of older people in a UK cohort with or at risk of musculoskeletal problems or frailty (Investigating Musculoskeletal Health and Wellbeing study), used multivariable logistic regression and Z-tests to assess the degrees of associations of pain (McGill Pain Rating Index), and painful and non-painful morbidity counts with frailty (modified FRAIL questionnaire).

RESULTS

Data were from 2,185 participants, 56% female, median age 73 (range 60 to 96) years. 430 (20%) participants were classified as frail. In a fully adjusted standardised model, pain (aOR 2.07 (95%CI 1.83 to 2.33) and 'any' morbidity aOR (1.74 (95%CI 1.54 to 1.97) were both significantly associated with frailty. When morbidity was subclassified as painful or non-painful, painful (aOR 1.48 (95%CI 1.30 to 1.68) and non-painful (aOR1.39 (95%CI 1.24 to 1.56)) morbidities each were associated with frailty, as also was pain (aOR 2.07 (95%CI 1.83 to 2.34, p < 0.001).

CONCLUSIONS

Pain is associated with frailty, over and above any effect of painful and non-painful morbidities. This forms the justification for future research which focuses on pain management in the identification, prevention, and treatment of frailty.

Effects of Analgesics on Self-Reported Physical Function and Walking Ability in People With Hip or Knee Osteoarthritis: A Systematic Review and Meta-Analysis

OBJECTIVE

Hip and knee osteoarthritis are among the leading causes of global disability, and one of the main aims of the management is to improve physical function. The objective of this review was to investigate the effect of analgesics on physical function (self-reported physical function and walking ability).

METHODS

A systematic review and meta-analysis of the findings were performed. Randomized controlled trials investigating the effect of analgesics on self-reported physical function and walking ability were included. Analgesics were orally administered acetaminophen, nonsteroidal antiinflammatory drugs (NSAIDs), or opioids. Data were pooled in a random-effects model, and the standardized mean difference (SMD) with 95% CI was calculated (SMDs: 0.2-0.4 = small, 0.5-0.7 = medium, and ≥0.8 = large effect sizes). The quality of the evidence was evaluated according to the Grading of Recommendations Assessment, Development, and Evaluation approach.

RESULTS

A total of 1454 studies were identified, of which 33 were included. On self-reported physical function, the results showed low- to moderate-quality evidence for a small beneficial effect of acetaminophen (SMD = -0.13 [95% CI = -0.26 to 0.00]), NSAIDs (SMD = -0.32 [95% CI = -0.37 to -0.27]), or opioids (SMD = -0.20 [95% CI = -0.32 to -0.09]). There was moderate-quality evidence for a small effect of NSAIDs on pain during walking (SMD = -0.34 [95% CI = -0.45 to -0.23]).

CONCLUSION

In people with hip or knee osteoarthritis, there was low- to moderate-quality evidence for small beneficial effects of analgesics on physical function and walking ability.

IMPACT

Analgesics may improve physical function by reducing pain during exercise and walking.

A multiyear time series (2004-2012) of bacterial and archaeal community dynamics in a changing Arctic Ocean

Climate change is profoundly impacting the Arctic, leading to a loss of multiyear sea ice and a warmer, fresher upper Arctic Ocean. The response of microbial communities to these climate-mediated changes is largely unknown. Here, we document the interannual variation in bacterial and archaeal communities across a 9-year time series of the Canada Basin that includes two historic sea ice minima (2007 and 2012). We report an overall loss of bacterial and archaeal community richness and significant shifts in community composition. The magnitude and period of most rapid change differed between the stratified water layers. The most pronounced changes in the upper water layers (surface mixed layer and upper Arctic water) occurred earlier in the time series, while changes in the lower layer (Pacific-origin water) occurred later. Shifts in taxonomic composition across time were subtle, but a decrease in Bacteroidota taxa and increase in Thaumarchaeota and Euryarchaeota taxa were the clearest signatures of change. This time series provides a rare glimpse into the potential influence of climate change on Arctic microbial communities; extension to the present day should contribute to deeper insights into the trajectory of Arctic marine ecosystems in response to warming and freshening.

The interrater and test-retest reliability of 3 modalities of quantitative sensory testing in healthy adults and people with chronic low back pain or rheumatoid arthritis

Introduction

Quantitative Sensory Testing (QST) modalities used to assess central pain mechanisms require different protocols in people with different musculoskeletal conditions.

Objectives

We aimed to explore the possible effects of musculoskeletal diagnosis and test site on QST interrater and test-retest reliability.

Methods

The study included participants with rheumatoid arthritis (RA, n = 18; QST conducted on lower leg) and low back pain (LBP, n = 25; QST conducted on forearm), plus 45 healthy control participants (n = 20 QST on lower leg and n = 25 QST on forearm). Test-retest reliability was assessed from QST conducted 1 to 3 weeks apart. Quantitative sensory testing modalities used were pressure pain detection threshold (PPT) at a site distant to tissue pathology, temporal summation (TS), and conditioned pain modulation (CPM). Temporal summation was calculated as difference or ratio of single and repeated punctate stimuli and unconditioned thresholds for CPM used single or mean of multiple PPTs. Intraclass correlation coefficients (ICCs) were compared between different subgroups.

Results

High to very high reliability was found for all assessments of PPT and TS across anatomical sites (lower leg and forearm) and participants (healthy, RA, and LBP) (ICC ≥ 0.77 for PPT and ICC ≥ 0.76 for TS). Reliability was higher when TS was calculated as a difference rather than a ratio. Conditioned pain modulation showed no to moderate reliability (ICC = 0.01-0.64) that was similar between leg or forearm, and between healthy people and those with RA or LBP.

Conclusion

PPT and TS are transferable tools to quantify pain sensitivity at different testing sites in different musculoskeletal diagnoses. Low apparent reliability of CPM protocols might indicate minute-to-minute dynamic pain modulation.

Chronic Low Back Pain with and without Concomitant Osteoarthritis: A Retrospective, Longitudinal Cohort Study of Patients in England

Objective

Despite the high prevalence of chronic low back pain (CLBP) and osteoarthritis (OA), few estimates of the economic cost of these conditions in England have been published. The aim of the present analysis was to characterise the economic burden of moderate-to-severe pain associated with CLBP + OA and CLBP alone compared with general population-matched controls without CLBP or OA. The primary objective was to describe the total healthcare resource use (HCRU) and direct healthcare costs associated with the target patient populations. Secondary objectives were to describe treatment patterns and surgical procedures.

Methods

This was a retrospective, observational cohort study of patients receiving healthcare indicative of moderate-to-severe chronic pain associated with CLBP, with or without OA. We used linked longitudinal data from the Clinical Practice Research Datalink GOLD and Hospital Episode Statistics (HES). Patients (cases) were matched 1 : 1 with controls on age, sex, comorbidity burden, GP practice, and HES data availability.

Results

The CLBP-alone cohort comprised 13 554 cases with CLBP and 13 554 matched controls; the CLBP + OA cohort comprised 7803 cases with both OA and CLBP and 7803 matched controls. Across all follow-up periods, patients with CLBP alone and those with CLBP + OA had significantly more GP consultations, outpatient attendances, emergency department visits, and inpatient stays than controls (all p < 0.0001). By 36 months after indexing, the mean (SD) per-patient total direct healthcare cost in the CLBP-alone cohort was £5081 (£5905) for cases and £1809 (£4451) for controls (p < 0.0001); in the CLBP + OA cohort, the mean (SD) per-patient total direct healthcare cost was £8819 (£7143) for cases and £2428 (£4280) for controls (p < 0.0001).

Conclusion

Moderate-to-severe chronic pain associated with CLBP-with or without OA-has a substantial impact on patients and healthcare providers, leading to higher HCRU and costs versus controls among people with CLBP alone or together with OA.

Association between pain intensity and depressive symptoms in community-dwelling adults: longitudinal findings from the Survey of Health, Ageing and Retirement in Europe (SHARE)

PURPOSE

To investigate the longitudinal associations between pain and depressive symptoms in adults.

METHODS

Prospective cohort study on data from 28,515 community-dwelling adults ≥ 50 years, free from depression at baseline (Wave 5), with follow-up in Wave 6 of the Survey of Health, Ageing and Retirement in Europe (SHARE). Significant depressive symptoms were defined by a EURO-D score ≥ 4. The longitudinal association between baseline pain intensity and significant depressive symptoms at follow-up was analysed using logistic regression models; odds ratios (ORs) and confidence intervals (CI) were calculated, adjusting for socio-demographic and clinical factors, physical inactivity, loneliness, mobility and functional impairments.

RESULTS

Mean age was 65.4 years (standard deviation 9.0, range 50-99); 14,360 (50.4%) participants were women. Mean follow-up was 23.4 (standard deviation 3.4) months. At baseline, 2803 (9.8%) participants reported mild pain, 5253 (18.4%) moderate pain and 1431 (5.0%) severe pain. At follow-up, 3868 (13.6%) participants-1451 (10.3%) men and 2417 (16.8%) women-reported significant depressive symptoms. After adjustment, mild, moderate and severe baseline pain, versus no pain, were associated with an increased likelihood of significant depressive symptoms at follow-up: ORs (95% CI) were 1.20 (1.06-1.35), 1.32 (1.20-1.46) and 1.39 (1.19-1.63), respectively. These associations were more pronounced in men compared to women, and consistent in participants aged 50-64 years, those without mobility or functional impairment, and those without loneliness at baseline.

CONCLUSION

Higher baseline pain intensity was longitudinally associated with a greater risk of significant depressive symptoms at 2-year follow-up, in community-dwelling adults without baseline depression.

A genome catalogue of lake bacterial diversity and its drivers at continental scale

Lakes are heterogeneous ecosystems inhabited by a rich microbiome whose genomic diversity is poorly defined. We present a continental-scale study of metagenomes representing 6.5 million km2 of the most lake-rich landscape on Earth. Analysis of 308 Canadian lakes resulted in a metagenome-assembled genome (MAG) catalogue of 1,008 mostly novel bacterial genomospecies. Lake trophic state was a leading driver of taxonomic and functional diversity among MAG assemblages, reflecting the responses of communities profiled by 16S rRNA amplicons and gene-centric metagenomics. Coupling the MAG catalogue with watershed geomatics revealed terrestrial influences of soils and land use on assemblages. Agriculture and human population density were drivers of turnover, indicating detectable anthropogenic imprints on lake bacteria at the continental scale. The sensitivity of bacterial assemblages to human impact reinforces lakes as sentinels of environmental change. Overall, the LakePulse MAG catalogue greatly expands the freshwater genomic landscape, advancing an integrative view of diversity across Earth's microbiomes.

Associations of Muscle Strength with Central Aspects of Pain: Data from the Knee Pain and Related Health in the Community (KPIC) Cohort

Knee pain is associated with lower muscle strength, and both contribute to disability. Peripheral and central neurological mechanisms contribute to OA pain. Understanding the relative contributions of pain mechanisms to muscle strength might help future treatments. The Knee Pain and related health In the Community (KPIC) cohort provided baseline and year 1 data from people with early knee pain (n = 219) for longitudinal analyses. A cross-sectional analysis was performed with baseline data from people with established knee pain (n = 103) and comparative data from people without knee pain (n = 98). Quadriceps and handgrip strength indicated local and general muscle weakness, respectively. The indices of peripheral nociceptive drive were knee radiographic and ultrasound scores. The indices associated with central pain mechanisms were Pressure Pain detection Threshold (PPT) distal to the knee, and a validated self-report Central Aspects of Pain Factor (CAPF). The associations were explored using correlation and multivariable regression. Weaker quadriceps strength was associated with both high CAPF and low PPT at baseline. Year 1 quadriceps weakness was predicted by higher baseline CAPF (β = -0.28 (95% CI: -0.55, -0.01), p = 0.040). Weaker baseline and year 1 handgrip strength was also associated with higher baseline CAPF. Weaker baseline quadriceps strength was associated with radiographic scores in bivariate but not adjusted analyses. Quadriceps strength was not significantly associated with total ultrasound scores. Central pain mechanisms might contribute to muscle weakness, both locally and remote from the knee.

Feasibility of conducting a cohort randomised controlled trial assessing the effectiveness of a nurse-led package of care for knee pain

OBJECTIVE

To evaluate the feasibility of conducting a cohort randomised-controlled trial (RCT) of a nurse-led package of care for knee pain and determine treatment sequence for use in a future trial.

METHODS

Open label, three-arm, single-centre, mixed-methods, feasibility cohort RCT. Adults aged ≥40 years with moderate-to-severe knee pain for ≥3 months were eligible. Participants were randomised into groups A (non-pharmacological treatment first), B (pharmacological treatment first), or group C (usual care). The intervention was delivered over 26-weeks. Outcomes were dropout rate, recruitment rate, intervention fidelity, ability to collect outcome data and treatment acceptability.

RESULTS

Seventeen participants were randomised and enrolled into each of groups A and B (5.2% recruitment rate), and 174 randomised to group C. Participant characteristics at randomisation were comparable across the three arms. COVID-19 paused the study from March-November-2020. Participants enrolled in groups A and B before March-2020 were withdrawn at restart. Of the 20 participants enrolled after restart, 18 completed the study (10% dropout). The nurse reported delivering most aspects of the intervention with high fidelity. Participants viewed the package of care as structured, supportive and holistic, they learnt about self-managing knee pain, and could engage with and follow the non-pharmacological treatment. Most found the non-pharmacological treatment more useful than the pharmacological treatment, preferring to receive it before or alongside analgesia. Many self-reported questionnaires were not fully completed.

CONCLUSIONS

The nurse-led package of care for knee pain was acceptable with low dropout, although the cohort RCT design may not be feasible for a definitive trial.

TRIAL REGISTRATION

clinicaltrials.gov; NCT03670706.

Serum Metabolome Analysis Identified Amino-Acid Metabolism Associated With Pain in People With Symptomatic Knee Osteoarthritis - A Cross-Sectional Study

Osteoarthritis (OA) is the most common arthritis affecting synovial joints such as knees and hips of millions of people globally. Usage-related joint pain and reduced function are the most common symptoms experienced by people with OA. To improve pain management, there is a need to identify validated biomarkers predicting therapeutic responses in targeted clinical trials. Our study aimed to identify the metabolic biomarkers for pain and pressure pain detection thresholds (PPTs) in participants with knee pain and symptomatic OA using metabolic phenotyping. Metabolite and cytokine measurements were done on serum samples using LC-MS/MS (liquid gas chromatography integrated magnetic resonance mass spectrometry) and Human Proinflammatory panel 1 kit respectively. Regression analysis was done in a test (n = 75) and replication study (n = 79) to investigate the metabolites associated with current knee pain scores and pressure pain detection thresholds (PPTs). Meta-analysis and correlation were done estimating precision of associated metabolites and identifying relationship between significant metabolites and cytokines respectively. Acyl ornithine, carnosine, cortisol, cortisone, cystine, DOPA, glycolithocholic acid sulphate (GLCAS), phenylethylamine (PEA) and succinic acid were found to be significantly (FDR <.1) associated with pain scores in meta-analysis of both studies. IL-10, IL-13, IL-1β, IL2, IL8 and TNF-α were also found to be associated with the significant metabolites. Significant associations of these metabolites and inflammatory markers with knee pain suggests that targeting relevant pathways of amino acid and cholesterol metabolism may modulate cytokines and these could be targeted as novel therapeutics development to improve knee pain and OA management. PERSPECTIVE: Foreseeing the global burden of knee pain in Osteoarthritis (OA) and adverse effects of current pharmacological therapies, this study is envisaged to investigate serum metabolites and molecular pathways involved in knee pain. The replicated metabolites in this study suggests targeting amino-acid pathways for better management of OA knee pain.

How people with knee pain understand why their pain changes or remains the same over time: A qualitative study

Objectives

Guidelines recommend knee osteoarthritis pain management based on biopsychosocial mechanisms. Treatment adherence and effectiveness may be affected if there is a mismatch between patient perspectives and treatment focus. We therefore examined patient perspectives on mechanisms of their knee pain, why it persisted or changed over the past year, whether their understanding had changed, and whether their understanding aligned with that of others with whom they interact.

Methods

Individuals with chronic knee pain (n ​= ​50) were purposively recruited from the Knee Pain and related health In the Community (KPIC) cohort to represent worsened, improved, or unchanged pain or anxiety between baseline and one year later. Framework analysis, a comparative form of thematic analysis, was used across transcripts of semi-structured telephone interviews.

Results

Data were collapsed into themes of diagnosis, joint structure, ageing, physical activity, weight management, and treatment. Participants focused on biomechanical rather than psychological pain mechanisms. Some participants attributed pain improvement to increased and others to decreased physical activity. Participants reported no change in their understanding of their pain during the preceding year, but that their attitudes to pain, for example acceptance, had changed. Participants reported that they and others around them lacked understanding of their pain and why it did or did not change.

Conclusion

People report a predominantly biomechanical understanding of why their knee pain remains constant or changes over time. Clinicians should support patients to develop a biopsychosocial understanding of knee pain aligned to treatment across the range of biological, psychological, and social modalities.

The bidirectional relationship between chronic joint pain and frailty: data from the Investigating Musculoskeletal Health and Wellbeing cohort

BACKGROUND

Pain and frailty are associated, but this relationship is insufficiently understood. We aimed to test whether there is a unidirectional or bidirectional relationship between joint pain and frailty.

METHODS

Data were from Investigating Musculoskeletal Health and Wellbeing, a UK-based cohort. Average joint pain severity over the previous month was assessed using an 11-point numerical rating scale (NRS). Frailty was classified as present/absent using the FRAIL questionnaire. Multivariable regression assessed the association between joint pain and frailty, adjusted for age, sex, and BMI class. Two-wave cross-lagged path modelling permitted simultaneous exploration of plausible causal pathways between pain intensity and frailty at baseline and 1-year. Transitions were assessed using t-tests.

RESULTS

One thousand one hundred seventy-nine participants were studied, 53% female, with a median age of 73 (range 60 to 95) years. FRAIL classified 176 (15%) participants as frail at baseline. Mean (SD) baseline pain score was 5.2 (2.5). Pain NRS ≥ 4 was observed in 172 (99%) of frail participants. Pain severity was associated with frailty at baseline (aOR 1.72 (95%CI 1.56 to 1.92)). In cross-lagged path analysis, higher baseline pain predicted 1-year frailty [β = 0.25, (95%CI 0.14 to 0.36), p < 0.001] and baseline frailty predicted higher 1-year pain [β = 0.06, (95%CI 0.003 to 0.11), p = 0.040]. Participants transitioning to frailty over one year had higher mean pain scores (6.4 (95%CI 5.8 to 7.1)) at baseline than those who remained non-frail (4.7 (95%CI 4.5 to 4.8)), p < 0.001.

CONCLUSIONS

The bidirectional relationship between pain and frailty could lead to a vicious cycle in which each accelerates the other's progression. This justifies attempts to prevent frailty by addressing pain and to include pain measures as an outcome in frailty studies.

Influence of Social Support, Financial Status, and Lifestyle on the Disparity Between Inflammation and Disability in Rheumatoid Arthritis

OBJECTIVE

To investigate how social support, financial status, and lifestyle influence the development of excess disability in rheumatoid arthritis (RA).

METHODS

Data were obtained from the Étude et Suivi des Polyarthrites Indifférenciées Récentes (ESPOIR) cohort study of people with RA. A previous analysis identified groups with similar inflammation trajectories but markedly different disability over 10 years; those in the higher disability trajectory groups were defined as having "excess disability." Self-reported data regarding contextual factors (social support, financial situation, lifestyle) were obtained from participants, and they completed patient-reported outcome measures (pain, fatigue, anxiety, depression) at baseline. The direct effect of the contextual factors on excess disability and the effect mediated by patient-reported outcome measures were assessed using structural equation models. Findings were validated in 2 independent data sets (Norfolk Arthritis Register [NOAR], Early Rheumatoid Arthritis Network [ERAN]).

RESULTS

Of 538 included ESPOIR participants (mean age ± SD 48.3 ± 12.2 years; 79.2% women), 200 participants (37.2%) were in the excess disability group. Less social support (β = 0.17 [95% confidence interval (95% CI) 0.08, 0.26]), worse financial situation (β = 0.24 [95% CI 0.14, 0.34]), less exercise (β = 0.17 [95% CI 0.09-0.25]), and less education (β = 0.15 [95% CI 0.06, 0.23]) were associated with excess disability group membership; smoking, alcohol consumption, and body mass index were not. Fatigue and depression mediated a small proportion of these effects. Similar results were seen in NOAR and ERAN.

CONCLUSION

Greater emphasis is needed on the economic and social contexts of individuals with RA at presentation; these factors might influence disability over the following decade.

Geospatial analysis reveals a hotspot of fecal bacteria in Canadian prairie lakes linked to agricultural non-point sources

Lakes are sentinels of environmental changes within their watersheds including those induced by a changing climate and anthropogenic activities. In particular, contamination originating from point or non-point sources (NPS) within watersheds might be reflected in changes in the bacterial composition of lake water. We assessed the abundance of potentially pathogenic bacteria (PPB) sampled in 413 lakes within 8 southern Canadian ecozones that represent a wide diversity of lakes and watershed land use. The study objectives were (1) to explore the diversity of PPB; (2) to build a fecal multi-indicator from a cluster of co-occurring PPB; and (3) to predict the fecal multi-indicator over thousands of lakes. We identified bacterial taxa based on 16S rRNA amplicon sequencing and clustered 33 PPB matching taxa in the Canadian ePATHogen database using a Sørensen dissimilarity index on binary data across the sampled lakes. One cluster contained Erysipelothrix, Desulfovibrio, Bacteroides, Vibrio and Acholeplasma and was related to the NPS fraction of agriculture and pasture within the watershed as its main driver and thus it was determined as the fecal multi-indicator. We subsequently developed a fecal multi-indicator predictive model across 200 212 southern Canadian lakes which explained 55.1% of the deviance. Mapping the predictions showed higher fecal multi-indicator abundances in the Prairies and Boreal Plains compared to the other ecozones. These results represent the first attempt to map a potential fecal multi-indicator at the continental scale, which may be further improved in the future. Lastly, the study demonstrates the capacity of a multi-disciplinary approach leveraging both datasets derived from remote sensing and DNA sequencing to provide mapping information for public health governmental policies.

1321 THE ASSOCIATION OF PAINFUL AND NON-PAINFUL COMORBIDITIES WITH FRAILTY

Introduction

Chronic pain is associated with frailty. We hypothesised that painful comorbidities would be more strongly associated with frailty than non-painful comorbidities.

Method

Data were from Investigating Musculoskeletal Health and Wellbeing, a UK-based cohort of people with or at risk of musculoskeletal problems or frailty. Average pain over the previous month was assessed using an 11-point numerical rating scale (NRS). The original FRAIL questionnaire comprises five self-report items: Fatigue, Resistance, Ambulation, Illnesses and Loss of weight. In this study risk of frailty was operationalised using a modified FRAIL questionnaire, omitting the “illnesses” item which related to comorbidities. Comorbidities were classified as either ‘painful’ or ‘non-painful’ based on the International Association for the Study of Pain chronic pain classification criteria. Ordinal logistic regression models explored associations of comorbidity counts with frailty.

Results

Cross-sectional data were from 2473 participants, 57% female, median age 72 (range 40 to 96) years. 518 (21%) participants were classified as frail. Mean (SD) pain score was 5.5 (2.5). Median (IQR) painful comorbidities was 2 (1 to 3) and non-painful 1 (0 to 2). Highest comorbidity frequency: arthritis (66%) and hypertension (38%). Pain was associated with frailty (OR 1.58 (1.52 to 1.64)). Painful comorbidities (aOR 1.64 (1.54 to 1.75) and non-painful comorbidities (aOR 1.31 (1.21 to 1.41)) were both associated with frailty when included in the same multivariable model adjusted for age, sex and BMI.

Conclusions

Painful comorbidities were most strongly associated with frailty, although non-painful comorbidities also contributed. Pain and frailty are interconnected, and this might in part be due to comorbidities or their treatments. These findings provide justification for further research to identify the mechanisms through which pain is involved in frailty and to include pain management in interventions to ameliorate frailty.

Chronic pain in people living with dementia: challenges to recognising and managing pain, and personalising intervention by phenotype

Pain is common in people with dementia, and pain can exacerbate the behavioural and psychological symptoms of dementia. Effective pain management is challenging, not least in people with dementia. Impairments of cognition, communication and abstract thought can make communicating pain unreliable or impossible. It is unclear which biopsychosocial interventions for pain management are effective in people with dementia, and which interventions for behavioural and psychological symptoms of dementia are effective in people with pain. The result is that drugs, physical therapies and psychological therapies might be either underused or overused. People with dementia and pain could be helped by assessment processes that characterise an individual's pain experience and dementia behaviours in a mechanistic manner, phenotyping. Chronic pain management has moved from a 'one size fits all' approach, towards personalised medicine, where interventions recommended for an individual depend upon the key mechanisms underlying their pain, and the relative values they place on benefits and adverse effects. Mechanistic phenotyping through careful personalised evaluation would define the mechanisms driving pain and dementia behaviours in an individual, enabling the formulation of a personalised intervention strategy. Central pain processing mechanisms are particularly likely to be important in people with pain and dementia, and interventions to accommodate and address these may be particularly helpful, not only to relieve pain but also the symptoms of dementia.

Osteoarthritis Bone Marrow Lesions

Assessment and treatment of Bone Marrow Lesions (BMLs) could ultimately make step changes to the lives of people with osteoarthritis (OA). We here review the imaging and pathological characteristics of OA-BMLs, their differential diagnosis and measurement, and cross-sectional and longitudinal associations with pain and OA structural progression. We discuss how biomechanical and cellular factors may contribute to BML pathogenesis, and how pharmacological and non-pharmacological interventions that target BMLs might reduce pain and OA structural progression. We critically appraise semiquantitative and quantitative methods for assessing BMLs, and their potential utilities for identifying people at risk of symptomatic and structural OA progression, and evaluating treatment responses. New interventions that target OA-BMLs should both confirm their importance, and reduce the unacceptable burden of OA.

Harmonising knee pain patient-reported outcomes: a systematic literature review and meta-analysis of Patient Acceptable Symptom State (PASS) and individual participant data (IPD)

OBJECTIVE

In order to facilitate data pooling between studies, we explored harmonisation of patient-reported outcome measures (PROMs) in people with knee pain due to osteoarthritis or knee trauma, using the Patient Acceptable Symptom State scores (PASS) as a criterion.

METHODS

We undertook a systematic literature review (SLR) of PASS scores, and performed individual participant data (IPD) analysis of score distributions from concurrently completed PROM pairs. Numerical rating scales (NRS), visual analogue scales, KOOS and WOMAC pain questionnaires were standardised to 0 to 100 (worst) scales. Meta-regression explored associations of PASS. Bland Altman plots compared PROM scores within individuals using IPD from WebEx, KICK, MenTOR and NEKO studies.

RESULTS

SLR identified 18 studies reporting PASS in people with knee pain. Pooled standardised PASS was 27 (95% CI: 21 to 35; n = 6,339). PASS was statistically similar for each standardised PROM. Lower PASS was associated with lower baseline pain (β = 0.49, P = 0.01) and longer time from treatment initiation (Q = 6.35, P = 0.04). PASS scores were lowest in ligament rupture (12, 95% CI: 11 to 13), but similar between knee osteoarthritis (31, 95% CI: 26 to 36) and meniscal tear (27, 95% CI: 20 to 35). In IPD, standardised PROMs each revealed similar group mean scores, but scores within individuals diverged between PROMs (LoA between -7 to -38 and +25 to 52).

CONCLUSION

Different standardised PROMs give similar PASS thresholds in group data. PASS thresholds may be affected more by patient and treatment characteristics than between PROMs. However, different PROMs give divergent scores within individuals, possibly reflecting different experiences of pain.

Medio-dorsal thalamic dysconnectivity in chronic knee pain: A possible mechanism for negative affect and pain comorbidity

The reciprocal interaction between pain and negative affect is acknowledged but pain-related alterations in brain circuits involved in this interaction, such as the mediodorsal thalamus (MDThal), still require a better understanding. We sought to investigate the relationship between MDThal circuitry, negative affect and pain severity in chronic musculoskeletal pain. For these analyses, participants with chronic knee pain (CKP, n = 74) and without (n = 36) completed magnetic resonance imaging scans and questionnaires. Seed-based MDThal functional connectivity (FC) was compared between groups. Within CKP group, we assessed the interdependence of MDThal FC with negative affect. Finally, post hoc moderation analysis explored whether burden of pain influences affect-related MDThal FC. The CKP group showed altered MDThal FC to hippocampus, ventromedial prefrontal cortex and subgenual anterior cingulate. Furthermore, in CKP group, MDThal connectivity correlated significantly with negative affect in several brain regions, most notably the medial prefrontal cortex, and this association was stronger with increasing pain burden and absent in pain-free controls. In conclusion, we demonstrate mediodorsal thalamo-cortical dysconnectivity in chronic pain with areas linked to mood disorders and associations of MDThal FC with negative affect. Moreover, burden of pain seems to enhance affect sensitivity of MDThal FC. These findings suggest mediodorsal thalamic network changes as possible drivers of the detrimental interplay between chronic pain and negative affect.

Degradation pathways for organic matter of terrestrial origin are widespread and expressed in Arctic Ocean microbiomes

BACKGROUND

The Arctic Ocean receives massive freshwater input and a correspondingly large amount of humic-rich organic matter of terrestrial origin. Global warming, permafrost melt, and a changing hydrological cycle will contribute to an intensification of terrestrial organic matter release to the Arctic Ocean. Although considered recalcitrant to degradation due to complex aromatic structures, humic substances can serve as substrate for microbial growth in terrestrial environments. However, the capacity of marine microbiomes to process aromatic-rich humic substances, and how this processing may contribute to carbon and nutrient cycling in a changing Arctic Ocean, is relatively unexplored. Here, we used a combination of metagenomics and metatranscriptomics to assess the prevalence and diversity of metabolic pathways and bacterial taxa involved in aromatic compound degradation in the salinity-stratified summer waters of the Canada Basin in the western Arctic Ocean.

RESULTS

Community-scale meta-omics profiling revealed that 22 complete pathways for processing aromatic compounds were present and expressed in the Canada Basin, including those for aromatic ring fission and upstream funneling pathways to access diverse aromatic compounds of terrestrial origin. A phylogenetically diverse set of functional marker genes and transcripts were associated with fluorescent dissolved organic matter, a component of which is of terrestrial origin. Pathways were common throughout global ocean microbiomes but were more abundant in the Canada Basin. Genome-resolved analyses identified 12 clades of Alphaproteobacteria, including Rhodospirillales, as central contributors to aromatic compound processing. These genomes were mostly restricted in their biogeographical distribution to the Arctic Ocean and were enriched in aromatic compound processing genes compared to their closest relatives from other oceans.

CONCLUSION

Overall, the detection of a phylogenetically diverse set of genes and transcripts implicated in aromatic compound processing supports the view that Arctic Ocean microbiomes have the capacity to metabolize humic substances of terrestrial origin. In addition, the demonstration that bacterial genomes replete with aromatic compound degradation genes exhibit a limited distribution outside of the Arctic Ocean suggests that processing humic substances is an adaptive trait of the Arctic Ocean microbiome. Future increases in terrestrial organic matter input to the Arctic Ocean may increase the prominence of aromatic compound processing bacteria and their contribution to Arctic carbon and nutrient cycles. Video Abstract.

Association of pain and risk of falls in community-dwelling adults: a prospective study in the Survey of Health, Ageing and Retirement in Europe (SHARE)

PURPOSE

To investigate the longitudinal associations between pain and falls risks in adults.

METHODS

Prospective cohort study on data from 40,636 community-dwelling adults ≥ 50 years assessed in Wave 5 and 6 in the Survey of Health, Ageing and Retirement in Europe (SHARE). Socio-demographic and clinical information was collected at baseline (Wave 5). At 2-year follow-up (Wave 6), falls in the previous 6 months were recorded. The longitudinal associations between pain intensity, number of pain sites and pain in specific anatomic sites, respectively, and falls risk were analysed by binary logistic regression models; odds ratios (95% confidence intervals) were calculated. All analyses were adjusted for socio-demographic and clinical factors and stratified by sex.

RESULTS

Mean age was 65.8 years (standard deviation 9.3; range 50-103); 22,486 (55.3%) participants were women. At follow-up, 2805 (6.9%) participants reported fall(s) in the previous 6 months. After adjustment, participants with moderate and severe pain at baseline had an increased falls risk at follow-up of 1.35 (1.21-1.51) and 1.52 (1.31-1.75), respectively, compared to those without pain (both p < 0.001); mild pain was not associated with falls risk. Associations between pain intensity and falls risk were greater at younger age (p for interaction < 0.001). Among participants with pain, pain in ≥ 2 sites or all over (multisite pain) was associated with an increased falls risk of 1.29 (1.14-1.45) compared to pain in one site (p < 0.001).

CONCLUSIONS

Moderate, severe and multisite pain were associated with an increased risk of subsequent falls in adults.

Interplay between cellular changes in the knee joint, circulating lipids and pain behaviours in a slowly progressing murine model of osteoarthritis

BACKGROUND

Synovial inflammation has known contributions to chronic osteoarthritis (OA) pain, but the potential role in transitions from early to late stages of OA pain is unclear.

METHODS

The slowly progressing surgical destabilization of the medial meniscus (DMM) murine OA model and sham control, was used in male C57BL/6J mice to investigate the interplay between knee inflammation, plasma pro- and anti-inflammatory oxylipins and pain responses during OA progression. Changes in joint histology, macrophage infiltration, chemokine receptor CX3CR1 expression, weight bearing asymmetry, and paw withdrawal thresholds were quantified 4, 8 and 16 weeks after surgery. Plasma levels of multiple bioactive lipid mediators were quantified using liquid chromatography with tandem mass-spectrometry (LC-MS/MS).

RESULTS

Structural joint damage was evident at 8 weeks post-DMM surgery onwards. At 16 weeks post-DMM surgery, synovial scores, numbers of CD68 and CD206 positive macrophages and pain responses were significantly increased. Plasma levels of oxylipins were negatively correlated with joint damage and synovitis scores at 4 and 8 weeks post-DMM surgery. Higher circulating levels of the pro-resolving oxylipin pre-cursor 17-HDHA were associated with lower weight bearing asymmetry at week 16.

CONCLUSIONS

The transition to chronic OA pathology and pain is likely influenced by both joint inflammation and plasma oxylipin mediators of inflammation and levels of pro-resolution molecules.

SIGNIFICANCE

Using a slow progressing surgical model of osteoarthritis we show how the changing balance between local and systemic inflammation may be of importance in the progression of pain behaviours during the transition to chronic osteoarthritis pain.

A resistome survey across hundreds of freshwater bacterial communities reveals the impacts of veterinary and human antibiotics use

Our decreasing ability to fight bacterial infections is a major health concern. It is arising due to the evolution of antimicrobial resistance (AMR) in response to the mis- and overuse of antibiotics in both human and veterinary medicine. Lakes integrate watershed processes and thus may act as receptors and reservoirs of antibiotic resistance genes (ARGs) introduced into the watershed by human activities. The resistome – the diversity of ARGs – under varying anthropogenic watershed pressures has been previously studied either focused on few select genes or few lakes. Here, we link the resistome of ~350 lakes sampled across Canada to human watershed activity, trophic status, as well as point sources of ARG pollution including wastewater treatment plants and hospitals in the watershed. A high percentage of the resistance genes detected was either unimpacted by human activity or highly prevalent in pristine lakes, highlighting the role of AMR in microbial ecology in aquatic systems, as well as a pool of genes available for potential horizontal gene transfer to pathogenic species. Nonetheless, watershed agricultural and pasture area significantly impacted the resistome. Moreover, the number of hospitals and the population density in a watershed, the volume of wastewater entering the lake, as well as the fraction of manure applied in the watershed as fertilizer significantly impacted ARG diversity. Together, these findings indicate that lake resistomes are regularly stocked with resistance genes evolved in the context of both veterinary and human antibiotics use and represent reservoirs of ARGs that require further monitoring.

Time course and localization of nerve growth factor expression and sensory nerve growth during progression of knee osteoarthritis in rats

OBJECTIVES

Nerve growth factor (NGF) and sensory nerves are key factors in established osteoarthritis (OA) knee pain. We investigated the time course of NGF expression and sensory nerve growth across early and late stages of OA progression in rat knees.

DESIGN

Knee OA was induced by medial meniscectomy in rats. OA histopathology, NGF expression, and calcitonin gene-related peptide immunoreactive (CGRP-IR) nerves were quantified pre-surgery and post-surgery at weeks 1, 2, 4 and 6. Pain-related behavior was evaluated using dynamic weight distribution and mechanical sensitivity of the hind paw.

RESULTS

NGF expression in chondrocytes increased from week 1 and remained elevated until the advanced stage. In synovium, NGF expression increased only in early stages, whereas in osteochondral channels and bone marrow, NGF expression increased in the later stages of OA progression. CGRP-IR nerve density in suprapatellar pouch peaked at week 4 and decreased at week 6, whereas in osteochondral channels and bone marrow, CGRP-IR innervation increased through week 6. Percent ipsilateral weight-bearing decreased throughout the OA time course, whereas reduced paw withdrawal thresholds were observed only in later stages.

CONCLUSION

During progression of knee OA, time-dependent alterations of NGF expression and CGRP-IR sensory innervation are knee tissue specific. NGF expression increased in early stages and decreased in advanced stage in the synovium but continued to increase in osteochondral channels and bone marrow. Increases in CGRP- IR sensory innervation followed increases in NGF expression, implicating that NGF is a key driver of articular nerve growth associated with OA pain.

Comorbidities and use of analgesics in people with knee pain: a study in the Nottingham Knee Pain and Health in the Community (KPIC) cohort

Objectives

The aims were to examine the prevalence of comorbidities and role of oral analgesic use in people with knee pain (KP) compared with those without.

Methods

The Knee Pain and related health In the Community (KPIC) cohort comprises community-derived adults aged ≥40 years, irrespective of knee pain. Thirty-six comorbidities across 10 systems were compared between people with KP and controls without KP or knee OA. Multivariable logistic regression analysis was used to determine the adjusted odds ratio (aOR) and 95% CI for multimorbidity (at least two chronic conditions) and each specific comorbidity. Both prescribed and over-the-counter analgesics were included in the model, and their interactions with KP for comorbidity outcomes were examined.

Results

Two thousand eight hundred and thirty-two cases with KP and 2518 controls were selected from 9506 baseline participants. The mean age of KP cases was 62.2 years, and 57% were women. Overall, 29% of the total study population had multimorbidity (KP cases 34.4%; controls 23.8%). After adjustment for age, sex, BMI and analgesic use, KP was significantly associated with multimorbidity (aOR 1.35; 95% CI 1.17, 1.56) and with cardiovascular (aOR 1.25; 95% CI 1.08, 1.44), gastrointestinal (aOR 1.34; 95% CI 1.04, 1.92), chronic widespread pain (aOR 1.54; 95% CI 1.29, 1.86) and neurological (aOR 1.32; 95% CI 1.01, 1.76) comorbidities. For multimorbidity, the use of paracetamol and opioids interacted positively with KP, whereas the use of NSAIDs interacted negatively for seven comorbidities.

Conclusion

People with KP are more likely to have other chronic conditions. The long-term benefits and harms of this change remain to be investigated.

Trial registration

ClinicalTrials.gov, http://clinicaltrials.gov, NCT02098070.

An observational study of centrally facilitated pain in individuals with chronic low back pain

Introduction

Central pain facilitation can hinder recovery in people with chronic low back pain (CLBP).

Objectives

The objective of this observational study was to investigate whether indices of centrally facilitated pain are associated with pain outcomes in a hospital-based cohort of individuals with CLBP undertaking a pain management programme.

Methods

Participants provided self-report and pain sensitivity data at baseline (n = 97) and again 3 months (n = 87) after a cognitive behavioural therapy-based group intervention including physiotherapy. Indices of centrally facilitated pain were pressure pain detection threshold, temporal summation and conditioned pain modulation at the forearm, Widespread Pain Index (WPI) classified using a body manikin, and a Central Mechanisms Trait (CMT) factor derived from 8 self-reported characteristics of anxiety, depression, neuropathic pain, fatigue, cognitive dysfunction, pain distribution, catastrophizing, and sleep. Pain severity was a composite factor derived from Numerical Rating Scales. Cross-sectional and longitudinal regression models were adjusted for age and sex.

Results

Baseline CMT and WPI each was associated with higher pain severity (CMT: r = 0.50, P < 0.001; WPI: r = 0.21, P = 0.04) at baseline and at 3 months (CMT: r = 0.38, P < 0.001; WPI: r = 0.24, P = 0.02). High baseline CMT remained significantly associated with pain at 3 months after additional adjustment for baseline pain (β = 2.45, P = 0.04, R 2 = 0.25, P < 0.0001). Quantitative sensory testing indices of pain hypersensitivity were not significantly associated with pain outcomes at baseline or at 3 months.

Conclusion

Central mechanisms beyond those captured by quantitative sensory testing are associated with poor CLBP outcome and might be targets for improved therapy.

The osteoarthritis bone score (OABS): a new histological scoring system for the characterisation of bone marrow lesions in osteoarthritis

OBJECTIVES

Bone marrow lesions (BMLs) are associated with pain in osteoarthritis (OA), but histological scores for OA focus on cartilage pathology. We developed a new scoring system, the Osteoarthritis Bone Score (OABS), to characterise OA-related BMLs.

METHODS

BML/non-BML tissues identified by Magnetic Resonance Imaging (MRI) in 10 knee OA subjects were harvested at total knee replacement (TKR). Osteochondral tissue from a further 140 TKR and 23 post-mortem (PM) cases was assessed. Histological features distinguishing MRI-defined BML/non-BML tissues on qualitative analysis were classified as present (0) or absent (1), summated for the OABS, validated by Rasch analysis and sensitivity to distinguish between sample groups. Immunohistochemistry for PGP9.5 assessed innervation.

RESULTS

Subchondral characteristics associated with BML tissues were cysts, fibrosis, hypervascularity, cartilage islands, trabecular thickening, loss of tidemark integrity and inflammatory cell infiltration. PGP9.5 immunoreactive perivascular nerves were associated with BMLs. OABS performed well as a measurement tool, displayed good reliability (Cronbach alpha = 0.68), had a 2-factor structure (trabecular/non-trabecular), with moderate correlation between the two factors (r = 0.56, 95% CI 0.46, 0.65). OABS scores were higher in TKR than PM cases with chondropathy, median difference 1.5 (95% CI -2, 0). OABS and Mankin scores similarly distinguished TKR from non-OA controls, but only OABS was higher in BML than non-BML tissues, median difference -4 (95% CI -5 to -2).

CONCLUSIONS

OABS identifies and validly quantifies histopathological changes associated with OA BMLs. Histopathology underlying BMLs may represent 2 inter-related pathological processes affecting trabecular/non-trabecular structures. Increased vascularity/perivascular innervation in BMLs might contribute to pain.

Clinical and Preclinical Evidence for Roles of Soluble Epoxide Hydrolase in Osteoarthritis Knee Pain

OBJECTIVE

Chronic pain due to osteoarthritis (OA) is a major clinical problem, and existing analgesics often have limited beneficial effects and/or adverse effects, necessitating the development of novel therapies. Epoxyeicosatrienoic acids (EETs) are endogenous antiinflammatory mediators, rapidly metabolized by soluble epoxide hydrolase (EH) to dihydroxyeicosatrienoic acids (DHETs). We undertook this study to assess whether soluble EH-driven metabolism of EETs to DHETs plays a critical role in chronic joint pain associated with OA and provides a new target for treatment.

METHODS

Potential associations of chronic knee pain with single-nucleotide polymorphisms (SNPs) in the gene-encoding soluble EH and with circulating levels of EETs and DHETs were investigated in human subjects. A surgically induced murine model of OA was used to determine the effects of both acute and chronic selective inhibition of soluble EH by N-[1-(1-oxopropy)-4-piperidinyl]-N'-(trifluoromethoxy)phenyl]-urea (TPPU) on weight-bearing asymmetry, hind paw withdrawal thresholds, joint histology, and circulating concentrations of EETs and DHETs.

RESULTS

In human subjects with chronic knee pain, 3 pain measures were associated with SNPs of the soluble EH gene EPHX2, and in 2 separate cohorts of subjects, circulating levels of EETs and DHETs were also associated with 3 pain measures. In the murine OA model, systemic administration of TPPU both acutely and chronically reversed established pain behaviors and decreased circulating levels of 8,9-DHET and 14,15-DHET. EET levels were unchanged by TPPU administration.

CONCLUSION

Our novel findings support a role of soluble EH in OA pain and suggest that inhibition of soluble EH and protection of endogenous EETs from catabolism represents a potential new therapeutic target for OA pain.

Exploring the disparity between inflammation and disability in the 10-year outcomes of people with rheumatoid arthritis

OBJECTIVES

To identify groups of people with RA with different disability trajectories over 10 years, despite comparable levels of inflammation.

METHODS

Data for this analysis came from three European prospective cohort studies of people with RA [Norfolk Arthritis Register (NOAR), Early RA Network (ERAN), Étude et Suivi des Polyarthrites Indifférenciées Récentes (ESPOIR)]. Participants were assessed regularly over 8 (ERAN) to 10 (NOAR/ESPOIR) years. Inclusion criteria were: recruited after 1 January 2000, <24 months baseline symptom duration, and disability (HAQ) and inflammation [two-component DAS28 (DAS28-2C)] recorded at baseline and at one other follow-up. People in each cohort also completed patient-reported outcome measures at each assessment (pain, fatigue, depressive symptoms). Group-based trajectory models were used to identify distinct groups of people with similar HAQ and DAS28-2C trajectories over follow-up.

RESULTS

This analysis included 2500 people with RA (NOAR: 1000, ESPOIR: 766, ERAN: 734). ESPOIR included more women and the participants were younger [mean (standard deviation) age: NOAR: 57.1 (14.6), ESPOIR: 47.6 (12.5), ERAN: 56.8 (13.8); women: NOAR: 63.9%, ESPOIR: 76.9%, ERAN: 69.1%). Within each cohort, two pairs of trajectories following the hypothesized pattern (comparable DAS28-2Cs but different HAQs) were identified. Higher pain, fatigue and depressive symptoms were associated with increased odds of being in the high HAQ trajectories.

CONCLUSION

Excess disability is persistent in RA. Controlling inflammation may not be sufficient to alleviate disability in all people with RA, and effective pain, fatigue and mood management may be needed in some groups to improve long-term function.

Exploring patient preference heterogeneity for pharmacological treatments for chronic pain: A latent class analysis

BACKGROUND

Several pharmaceutical treatments for chronic pain caused by osteoarthritis (OA) and chronic low back pain (CLBP) are available or currently under development, each associated with different adverse events (AEs) and efficacy profiles. It is therefore important to understand what trade-offs patients are willing to make when choosing between treatments.

METHODS

A discrete-choice experiment (DCE) was conducted with 437 adults with chronic pain caused by OA and/or CLBP. Respondents were presented with a series of scenarios and asked to choose between pairs of hypothetical treatments, each defined by six attributes: level of symptom control; risks of heart attack, rapidly progressive osteoarthritis and dependency; frequency and mode of administration and cost. Attributes were based on known profiles of oral nonsteroidal anti-inflammatory drugs, opioids and injected nerve growth factor inhibitors, the last of which were under clinical development at the time of the study. Data were analysed using a latent class (LC) model to explore preference heterogeneity.

RESULTS

Overall, respondents considered improving symptom control and reducing risk of physical dependency to be the most important attributes. The LC analysis identified four participant classes: an 'efficacy-focused' class (33.7%), a 'cost-averse' class (29.4%), a 'physical-dependence-averse' class (19.6%) and a 'needle-averse' class (17.3%). Subgroup membership was incompletely predicted by participant age and their responses to comprehension questions.

CONCLUSIONS

Preference heterogeneity across respondents indicates a need for a personalized approach to offering treatment options. Symptom improvement, cost, physical dependence and route of administration might be important to different patients.

SIGNIFICANCE

Multiple treatment options that differ substantially in terms of efficacy and adverse events are available for the management of chronic pain. With a growing emphasis on a patient-centred care model that incorporates patients' priorities and values into treatment decisions, there is a need to understand how individuals with chronic musculoskeletal pain balance the benefits and risks of treatment and how treatment priorities vary among individuals. This study was designed to identify patient preferences for different characteristics of treatments for the management of chronic pain and to investigate how preferences differ among respondents.

Comparing microscopy and DNA metabarcoding techniques for identifying cyanobacteria assemblages across hundreds of lakes

Accurately identifying the species present in an ecosystem is vital to lake managers and successful bioassessment programs. This is particularly important when monitoring cyanobacteria, as numerous taxa produce toxins and can have major negative impacts on aquatic ecosystems. Increasingly, DNA-based techniques such as metabarcoding are being used for measuring aquatic biodiversity, as they could accelerate processing time, decrease costs and reduce some of the biases associated with traditional light microscopy. Despite the continuing use of traditional microscopy and the growing use of DNA metabarcoding to identify cyanobacteria assemblages, methodological comparisons between the two approaches have rarely been reported from a wide suite of lake types. Here, we compare planktonic cyanobacteria assemblages generated by inverted light microscopy and DNA metabarcoding from a 379-lake dataset spanning a longitudinal and trophic gradient. We found moderate levels of congruence between methods at the broadest taxonomic levels (i.e., Order, RV=0.40, p < 0.0001). This comparison revealed distinct cyanobacteria communities from lakes of different trophic states, with Microcystis, Aphanizomenon and Dolichospermum dominating with both methods in eutrophic and hypereutrophic sites. This finding supports the use of either method when monitoring eutrophication in lake surface waters. The biggest difference between the two methods was the detection of picocyanobacteria, which are typically underestimated by light microscopy. This reveals that the communities generated by each method currently are complementary as opposed to identical and promotes a combined-method strategy when monitoring a range of trophic systems. For example, microscopy can provide measures of cyanobacteria biomass, which are critical data in managing lakes. Going forward, we believe that molecular genetic methods will be increasingly adopted as reference databases are routinely updated with more representative sequences and will improve as cyanobacteria taxonomy is resolved with the increase in available genetic information.

Identifying multiple knee pain trajectories and the prediction of opioid and NSAID medication used: A latent class growth approach

BACKGROUND

Knee pain is a major source of distress and disability, with pain progression highly variable between individuals. Previous studies defining pain trajectories have all used a single measure of pain, and these differ across studies. Different measures reflect diverse pain mechanisms. To ascertain the clinical utility of pain trajectories, we explored associations between opioid and non-steroidal anti-inflammatory drug (NSAID) use.

METHODS

We model pain trajectories using two measures-Intermittent and Constant Osteoarthritis Pain (ICOAP) and the painDETECT, in 2141 participants, across 3 waves (the baseline, 1- and 3-year assessments) of the Knee Pain In the Community (KPIC) cohort.

RESULTS

Latent class growth analysis identified six trajectories using ICOAP subscales (High-Stable, Low-Stable, Moderate Worsening, Moderate Recovering, Worsening, and Recovering) and four trajectories using painDETECT (High-stable, Low-stable, Moderate Worsening, and Moderate Recovering). There was a high degree of correspondence between people assigned to pain trajectories between ICOAP intermittent and constant subscales, but less so using painDETECT. Opioid use was associated with ICOAP trajectories only (e.g., High-Stable and Worsening intermittent ICOAP trajectories) and in women.

CONCLUSION

Different measures of pain produce different patterns of pain progression and these are differentially related to medication use. Opioid use is linked to trajectories of pain based on the impact of pain on behavior and not pain symptoms. Thus, managing pain's behavioral impact is more central to understanding opioid use than managing pain symptoms. These findings support more in-depth questioning about the type of pain and its progression in clinical practice.

The STAR care pathway for patients with pain at 3 months after total knee replacement: a multicentre, pragmatic, randomised, controlled trial

BACKGROUND

Approximately 20% of people experience chronic pain after total knee replacement, but effective treatments are not available. We aimed to evaluate the clinical effectiveness and cost-effectiveness of a new care pathway for chronic pain after total knee replacement.

METHODS

We did an unmasked, parallel group, pragmatic, superiority, randomised, controlled trial at eight UK National Health Service (NHS) hospitals. People with chronic pain at 3 months after total knee replacement surgery were randomly assigned (2:1) to the Support and Treatment After Replacement (STAR) care pathway plus usual care, or to usual care alone. The STAR intervention aimed to identify underlying causes of chronic pain and enable onward referrals for targeted treatment through a 3-month post-surgery assessment with an extended scope practitioner and telephone follow-up over 12 months. Co-primary outcomes were self-reported pain severity and pain interference in the replaced knee, assessed with the Brief Pain Inventory (BPI) pain severity and interference scales at 12 months (scored 0-10, best to worst) and analysed on an as-randomised basis. Resource use, collected from electronic hospital records and participants, was valued with UK reference costs. Quality-adjusted life-years (QALYs) were calculated from EQ-5D-5L responses. This trial is registered with ISRCTN, ISRCTN92545361.

FINDINGS

Between Sept 6, 2016, and May 31, 2019, 363 participants were randomly assigned to receive the intervention plus usual care (n=242) or to receive usual care alone (n=121). Participants had a median age of 67 years (IQR 61 to 73), 217 (60%) of 363 were female, and 335 (92%) were White. 313 (86%) patients provided follow-up data at 12 months after randomisation (213 assigned to the intervention plus usual care and 100 assigned to usual care alone). At 12 months, the mean between-group difference in the BPI severity score was -0·65 (95% CI -1·17 to -0·13; p=0·014) and the mean between-group difference in the BPI interference score was -0·68 (-1·29 to -0·08; p=0·026), both favouring the intervention. From an NHS and personal social services perspective, the intervention was cost-effective (greater improvement with lower cost), with an incremental net monetary benefit of £1256 (95% CI 164 to 2348) at £20 000 per QALY threshold. One adverse reaction of participant distress was reported in the intervention group.

INTERPRETATION

STAR is a clinically effective and cost-effective intervention to improve pain outcomes over 1 year for people with chronic pain at 3 months after total knee replacement surgery.

FUNDING

National Institute for Health Research.

Different genes may be involved in distal and local sensitisation: a genome-wide gene-based association study and meta-analysis

Background

Neuropathic pain symptoms and signs of increased pain sensitization in osteoarthritis (OA) patients may explain persistent pain after total joint replacement (TJR). Therefore, identifying genetic markers associated with pain sensitization and neuropathic‐like pain phenotypes could be clinically important in identifying targets for early intervention.

Methods

We performed a genome‐wide gene‐based association study (GWGAS) using pressure pain detection thresholds (PPTs) from distal pain‐free sites (anterior tibia), a measure of distal sensitization, and from proximal pain‐affected sites (lateral joint line), a measure of local sensitization, in 320 knee OA participants from the Knee Pain and related health in the Community (KPIC) cohort. We next performed gene‐based fixed‐effects meta‐analysis of PPTs and a neuropathic‐like pain phenotype using genome‐wide association study (GWAS) data from KPIC and from an independent cohort of 613 post‐TJR participants, respectively.

Results

The most significant genes associated with distal and local sensitization were OR5B3 and BRDT, respectively. We also found previously identified neuropathic pain‐associated genes—KCNA1, MTOR, ADORA1 and SCN3B—associated with PPT at the anterior tibia and an inflammatory pain gene—PTAFR—associated with PPT at the lateral joint line. Meta‐analysis results of anterior tibia and neuropathic‐like pain phenotypes revealed genes associated with bone morphogenesis, neuro‐inflammation, obesity, type 2 diabetes, cardiovascular disease and cognitive function.

Conclusions

Overall, our results suggest that different biological processes might be involved in distal and local sensitization, and common genetic mechanisms might be implicated in distal sensitization and neuropathic‐like pain. Future studies are needed to replicate these findings.

Significance

To the best of our knowledge, this is the first GWAS for pain sensitization and the first gene‐based meta‐analysis of pain sensitization and neuropathic‐like pain. Higher pain sensitization and neuropathic pain symptoms are associated with persistent pain after surgery hence, identifying genetic biomarkers and molecular pathways associated with these traits is clinically relevant.

Fidelity assessment of nurse-led non-pharmacological package of care for knee pain in the package development phase of a feasibility randomised controlled trial based in secondary care: a mixed methods study

OBJECTIVES

To evaluate fidelity of delivery of a nurse-led non-pharmacological complex intervention for knee pain.

SETTING

Secondary care. Single-centre study.

STUDY DESIGN

Mixed methods study.

PARTICIPANTS

Eighteen adults with chronic knee pain.

INCLUSION CRITERIA

Age >40 years, knee pain present for longer than 3 months, knee pain for most days of the previous month, at least moderate pain in two of the five domains of Western Ontario and McMaster Universities Osteoarthritis Index pain scale.

INTERVENTIONS

Nurse-led non-pharmacological intervention comprising assessment, education, exercise, use of hot/cold treatments, footwear modification, walking aids and weight-loss advice (if required).

OUTCOMES

Primary: fidelity of delivery of intervention, secondary: nurses' experience of delivering intervention.

METHODS

Each intervention session with every participant was video recorded and formed part of fidelity assessment. Fidelity checklists were completed by the research nurse after each session and by an independent researcher, after viewing the video-recordings blinded to nurse ratings. Fidelity scores (%), percentage agreement and 95% Confidence Intervals (CI) were calculated. Two semi-structured interviews were conducted with the research nurse.

RESULTS

Fourteen participants completed all visits. 62 treatment sessions took place. Nurse self-report and assessor video rating scores for all 62 treatment sessions were included in fidelity assessment. Overall fidelity was higher on nurse self-report (97.7%) than on objective video-rating (84.2%). Percentage agreement between nurse self-report and video-rating was 73.3% (95% CI 71.3 to 75.3). Fidelity was lowest for advice on footwear and walking aids. The nurse reported difficulty advising on thermal treatments, footwear and walking aids, and did not feel confident negotiating achievable and realistic goals with participants.

CONCLUSIONS

A trained research nurse can deliver most components of a non-pharmacological intervention for knee pain to a high degree of fidelity. Future research should assess intervention fidelity in a routine clinical setting, and examine its clinical and cost-effectiveness.

TRIAL REGISTRATION NUMBER

NCT03670706.

Rethinking microbial infallibility in the metagenomics era

The 'principle of microbial infallibility' was a mainstay of microbial physiology and environmental microbiology in earlier decades. This principle asserts that wherever there is an energetic gain to be made from environmental resources, microorganisms will find a way to take advantage of the situation. Although previously disputed, this claim was revived with the discovery of anammox bacteria and other major contributors to biogeochemistry. Here, we discuss the historical background to microbial infallibility, and focus on its contemporary relevance to metagenomics. Our analysis distinguishes exploration-driven metagenomics from hypothesis-driven metagenomics. In particular, we show how hypothesis-driven metagenomics can use background assumptions of microbial infallibility to enable the formulation of hypotheses to be tested by enrichment cultures. Discoveries of comammox and the anaerobic oxidation of methane are major instances of such strategies, and we supplement them with outlines of additional examples. This overview highlights one way in which metagenomics is making the transition from an exploratory data-analysis programme of research to a hypothesis-testing one. We conclude with a discussion of how microbial infallibility is a heuristic with far-reaching implications for the investigation of life.

The efficacy of systemic glucocorticosteroids for pain in rheumatoid arthritis: a systematic literature review and meta-analysis

Objectives

Glucocorticosteroids (GCs) are recommended to suppress inflammation in people with active RA. This systematic review and meta-analysis aimed to quantify the effects of systemic GCs on RA pain.

Methods

A systematic literature review of randomized controlled trials (RCTs) in RA comparing systemic GCs to inactive treatment. Three databases were and spontaneous pain and evoked pain outcomes were extracted. Standardized mean differences (SMDs) and mean differences were meta-analysed. Heterogeneity (I², tau statistics) and bias (funnel plot, Egger’s test) were assessed. Subgroup analyses investigated sources of variation. This study was pre-registered (PROSPERO CRD42019111562).

Results

A total of 18 903 titles, 880 abstracts and 226 full texts were assessed. Thirty-three RCTs suitable for the meta-analysis included 3123 participants. Pain scores (spontaneous pain) decreased in participants treated with oral GCs; SMD = −0.65 (15 studies, 95% CI −0.82, −0.49, P <0.001) with significant heterogeneity (I² = 56%, P =0.0002). Efficacy displayed time-related decreases after GC initiation. Mean difference visual analogue scale pain was −15 mm (95% CI −20, −9) greater improvement in GC than control at ≤3 months, −8 mm (95% CI −12, −3) at >3–6 months and −7 mm (95% CI −13, 0) at >6 months. Similar findings were obtained when evoked pain outcomes were examined. Data from five RCTs suggested improvement also in fatigue during GC treatment.

Conclusion

Oral GCs are analgesic in RA. The benefit is greatest shortly after initiation and GCs might not achieve clinically important pain relief beyond 3 months. Treatments other than anti-inflammatory GCs should be considered to reduce the long-term burden of pain in RA.

Central Aspects of Pain in Rheumatoid Arthritis (CAP-RA): protocol for a prospective observational study

BACKGROUND

Pain and fatigue are persistent problems in people with rheumatoid arthritis. Central sensitisation (CS) may contribute to pain and fatigue, even when treatment has controlled inflammatory disease. This study aims to validate a self-report 8-item questionnaire, the Central Aspects of Pain in Rheumatoid Arthritis (CAP-RA) questionnaire, developed to measure central pain mechanisms in RA, and to predict patient outcomes and response to treatment. A secondary objective is to explore mechanisms linking CS, pain and fatigue in people with RA.

METHODS/DESIGN

This is a prospective observational cohort study recruiting 250 adults with active RA in secondary care. The CAP-RA questionnaire, demographic data, medical history, and patient reported outcome measures (PROMs) of traits associated with central sensitization will be collected using validated questionnaires. Quantitative sensory testing modalities of pressure pain detection thresholds, temporal summation and conditioned pain modulation will be indices of central sensitization, and blood markers, swollen joints and ultrasound scans will be indices of inflammation. Primary data collection will be at baseline and 12 weeks. The test-retest reliability of CAP-RA questionnaire will be determined 1 week after the baseline visit. Pain and fatigue data will be collected weekly via text messages for 12 weeks. CAP-RA psychometric properties, and predictive validity for outcomes at 3 months will be evaluated.

DISCUSSION

This study will validate a simple self-report questionnaire against psychophysical indices of central sensitization and patient reported outcome measures of traits associated with CS in a population of individuals with active RA. The application of this instrument in the clinical environment could provide a mechanism-based stratification tool to facilitate the provision of targeted therapy to individuals with pain and fatigue in RA, alongside treatments that target joint inflammation.

TRIAL REGISTRATION

Clinicaltrials.gov NCT04515589 . Date of registration 17 August 2020.

Role of organic matter and microbial communities in mercury retention and methylation in sediments near run-of-river hydroelectric dams

Run-of-river power plants (RoRs) are expected to triple in number over the next decades in Canada. These structures are not anticipated to considerably promote the mobilization and transport of mercury (Hg) and its subsequent microbial transformation to methylmercury (MeHg), a neurotoxin able to biomagnify in food webs up to humans. To test whether construction of RoRs had an effect on Hg transport and transformation, we studied Hg and MeHg concentrations, organic matter contents and methylating microbial community abundance and composition in the sediments of a section of the St. Maurice River (Quebec, Canada). This river section has been affected by the construction of two RoR dams and its watershed has been disturbed by a forest fire, logging, and the construction of wetlands. Higher total Hg (THg) and MeHg concentrations were observed in the surface sediments of the flooded sites upstream of the RoRs. These peaks in THg and MeHg were correlated with organic matter proportions in the sediments (r² = 0.87 and 0.82, respectively). In contrast, the proportion of MeHg, a proxy for methylation potential, was best explained by the carbon to nitrogen ratio suggesting the importance of terrigenous organic matter as labile substrate for Hg methylation in this system. Metagenomic analysis of Hg-methylating communities based on the hgcA functional gene marker indicated an abundance of methanogens, sulfate reducers and fermenters, suggesting that these metabolic guilds may be primary Hg methylators in these surface sediments. We propose that RoR pondages act as traps for sediments, organic matter and Hg, and that this retention can be amplified by other disturbances of the watershed such as forest fire and logging. RoR flooded sites can be conducive to Hg methylation in sediments and may act as gateways for bioaccumulation and biomagnification of MeHg along food webs, particularly in disturbed watersheds.

Long-Term Safety and Efficacy of Subcutaneous Tanezumab Versus Nonsteroidal Antiinflammatory Drugs for Hip or Knee Osteoarthritis: A Randomized Trial

OBJECTIVE

To assess the long-term safety and 16-week efficacy of subcutaneous tanezumab in patients with hip or knee osteoarthritis (OA).

METHODS

This was a phase III randomized, double-blind, active treatment-controlled (using nonsteroidal antiinflammatory drugs [NSAIDs] as the active treatment control) safety trial of tanezumab (56-week treatment/24-week posttreatment follow-up) in adults who were receiving stable-dose NSAID therapy at the time of screening and who had Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain and physical function scores of ≥5; patient global assessment (PtGA) of OA of fair, poor, or very poor; history of inadequate pain relief with standard analgesics; and no history or radiographic evidence of prespecified bone/joint conditions beyond OA. Patients received oral naproxen, celecoxib, or diclofenac twice daily (NSAID group; n = 996) or tanezumab 2.5 mg (n = 1,002) or 5 mg (n = 998) subcutaneously every 8 weeks. Coprimary efficacy end points at week 16 were changes in WOMAC pain and physical function scores and changes in PtGA. The primary joint safety end point over 80 weeks comprised adjudicated rapidly progressive OA type 1 or 2, primary osteonecrosis, subchondral insufficiency fracture, or pathologic fracture. Mean values, least squares mean values, and least squares mean differences between groups (with 95% confidence intervals [95% CIs]) were calculated.

RESULTS

Of 3,021 randomized patients, 2,996 received ≥1 treatment dose. Adverse events (AEs) were similar between patients treated with tanezumab 2.5 mg and those treated with NSAIDs, and were more prevalent in those treated with tanezumab 5 mg. Composite joint safety events were significantly more prevalent with tanezumab 2.5 mg and tanezumab 5 mg than with NSAIDs (observation time-adjusted rate/1,000 patient-years 38.3 [95% CI 28.0, 52.5] and 71.5 [95% CI 56.7, 90.2], respectively, versus 14.8 [95% CI 8.9, 24.6]; P = 0.001 for tanezumab 2.5 mg versus NSAIDs; P < 0.001 for tanezumab 5 mg versus NSAIDs). Tanezumab 5 mg significantly improved pain and physical function but did not improve PtGA at week 16 when compared to NSAIDs; corresponding differences between the tanezumab 2.5 mg and NSAID groups were not statistically significant.

CONCLUSION

In patients previously receiving a stable dose of NSAIDs, tanezumab administered subcutaneously resulted in more joint safety events than continued NSAIDs, with differences being dose dependent. Pain and physical function improved with both doses of tanezumab compared to NSAIDs, reaching statistical significance with tanezumab 5 mg at 16 weeks.

The Central Aspects of Pain in the Knee (CAP-Knee) questionnaire; a mixed-methods study of a self-report instrument for assessing central mechanisms in people with knee pain

OBJECTIVES

Pain is the prevailing symptom of knee osteoarthritis. Central sensitisation creates discordance between pain and joint pathology. We previously reported a Central Pain Mechanisms trait derived from eight discrete characteristics: Neuropathic-like pain, Fatigue, Cognitive-impact, Catastrophising, Anxiety, Sleep disturbance, Depression, and Pain distribution. We here validate and show that an 8-item questionnaire, Central Aspects of Pain in the Knee (CAP-Knee) is associated both with sensory- and affective- components of knee pain severity.

METHODS

Participants with knee pain were recruited from the Investigating Musculoskeletal Health and Wellbeing study in the East Midlands, UK. CAP-Knee items were refined following cognitive interviews. Psychometric properties were assessed in 250 participants using Rasch-, and factor-analysis, and Cronbach's alpha. Intra-class correlation coefficients tested repeatability. Associations between CAP-Knee and McGill Pain questionnaire pain severity scores were assessed using linear regression.

RESULTS

CAP-Knee targeted the knee pain sample well. Cognitive interviews indicated that participants interpreted CAP-Knee items in diverse ways, which aligned to their intended meanings. Fit to the Rasch model was optimised by rescoring each item, producing a summated score from 0 to 16. Internal consistency was acceptable (Cronbach's alpha = 0.74) and test-retest reliability was excellent (ICC2,1 = 0.91). Each CAP-Knee item contributed uniquely to one discrete 'Central Mechanisms trait' factor. High CAP-Knee scores associated with worse overall knee pain intensity, and with each of sensory- and affective- McGill Pain Questionnaire scores.

CONCLUSION

CAP-Knee is a simple and valid self-report questionnaire, which measures a single 'Central Mechanisms' trait, and may help identify and target centrally-acting treatments aiming to reduce the burden of knee pain.

Microbial Diversity and Mercury Methylation Activity in Periphytic Biofilms at a Run-of-River Hydroelectric Dam and Constructed Wetlands

Periphytic biofilms have the potential to greatly influence the microbial production of the neurotoxicant monomethylmercury in freshwaters although few studies have simultaneously assessed periphyton mercury methylation and demethylation rates and the microbial communities associated with these transformations. We performed a field study on periphyton from a river affected by run-of-river power plants and artificial wetlands in a boreal landscape (Québec, Canada). In situ incubations were performed on three sites using environmental concentrations of isotopically enriched monomethylmercury (MM198Hg) and inorganic mercury (200Hg) for demethylation and methylation rate measurements. Periphytic microbial communities were investigated through 16S rRNA gene analyses and metagenomic screenings for the hgcA gene, involved in mercury methylation. Positive mercury methylation rates ([5.9 ± 3.4] × 10-3 day-1) were observed only in the wetlands, and demethylation rates averaged 1.78 ± 0.21 day-1 for the three studied sites. The 16S rRNA gene analyses revealed Proteobacteria as the most abundant phylum across all sites (36.3% ± 1.4%), from which families associated with mercury methylation were mostly found in the wetland site. Metagenome screening for HgcA identified 24 different hgcA sequences in the constructed wetland site only, associated with 8 known families, where the iron-reducing Geobacteraceae were the most abundant. This work brings new information on mercury methylation in periphyton from habitats of impacted rivers, associating it mostly with putative iron-reducing bacteria.IMPORTANCE Monomethylmercury (MMHg) is a biomagnifiable neurotoxin of global concern with risks to human health mostly associated with fish consumption. Hydroelectric reservoirs are known to be sources of MMHg many years after their impoundment. Little is known, however, on run-of-river dams flooding smaller terrestrial areas, although their numbers are expected to increase considerably worldwide in decades to come. Production of MMHg is associated mostly with anaerobic processes, but Hg methylation has been shown to occur in periphytic biofilms located in oxic zones of the water column. Therefore, in this study, we investigated in situ production of MMHg by periphytic communities in habitats impacted by the construction of a run-of-river dam by combining transformation rate measurements with genomic approaches targeting hgcAB genes, responsible for mercury methylation. These results provide extended knowledge on mercury methylators in river ecosystems impacted by run-of-river dams in temperate habitats.