C-reactive protein, APOE genotype and longitudinal cognitive change in an older population

C-reactive protein-mediated dementia

Loss of memory is the main feature of dementia, accompanied by personality changes. Alzheimer's disease (AD) is the most prevalent type of dementia globally and a major contributor to disability and mortality in older individuals. Most notably, the neurological damage caused by AD is irreversible, but the current market still lacks effective medications for the treatment of dementia. Numerous research studies have indicated that the inflammatory response is significantly involved in the development of cognitive impairment, and elevated C-reactive protein (CRP) levels in healthy people increases the likelihood of future AD. CRP is a nonspecific indicator of inflammation. In clinical practice, CRP has long been proven to be one of the risk factors and powerful predictors of neurodegenerative diseases. Given the accessibility and cost-effectiveness of CRP testing, it is reasonable to anticipate its utilisation for early screening and monitoring the progression of AD in the future. This review therefore focuses on the specific relationship between CRP and various types of dementia and explores how CRP contributes to cognitive impairment.

Longitudinal and concurrent C-reactive protein and diet associations with cognitive function in the population-based Tromsø study

BackgroundImmune dysregulation has been implicated in Alzheimer's disease; however, precise mechanisms and timing have not been established.ObjectiveTo investigate the concurrent and longitudinal associations of serum C-reactive protein (CRP) and dietary inflammatory index (DII) with cognitive decline as observed in Alzheimer's disease.MethodsThe study was based on 7613 individuals who participated in Tromsø6 (2007-2008) and Tromsø7 (2015-2016). We analyzed the relationship between CRP levels, DII, and cognitive function cross-sectionally using linear regression. We used mediation analysis to examine if CRP mediates the effects of DII on cognitive function. Further, we related baseline serum CRP to cognitive function and to change in cognitive function after 7 years of follow up. We used linear mixed models to relate changes in CRP levels to changes in cognitive function measured at two time points with 7 years apart.ResultsBoth CRP level and DII were cross-sectionally inversely associated with cognitive function (psychomotor speed, executive function). There was no prospective relationship between CRP level at baseline and cognitive function after 7 years of follow up. Increase in CRP levels was associated with decrease in cognitive function (psychomotor speed, executive function, and verbal memory) observed between two measurements 7 years apart. The mediation model did not show convincing evidence of a mediating effect of CRP in the association between diet and cognitive function.ConclusionsAfter comprehensive analysis of associations between CRP, DII and cognitive function, we conclude that CRP is likely to reflect the changes in inflammatory environment occurring in parallel with cognitive decline.

Longer sleep duration and neuroinflammation in at-risk elderly with a parental history of Alzheimer's disease

STUDY OBJECTIVES

Although short sleep could promote neurodegeneration, long sleep may be a marker of ongoing neurodegeneration, potentially as a result of neuroinflammation. The objective was to evaluate sleep patterns with age of expected Alzheimer's disease (AD) onset and neuroinflammation.

METHODS

We tested 203 dementia-free participants (68.5 ± 5.4 years old, 78M). The PREVENT-AD cohort includes older persons with a parental history of AD whose age was nearing their expected AD onset. We estimated expected years to AD onset by subtracting the participants' age from their parent's at AD dementia onset. We extracted actigraphy sleep variables of interest (times of sleep onset and morning awakening, time in bed, sleep efficiency, and sleep duration) and general profiles (sleep fragmentation, phase delay, and hypersomnia). Cerebrospinal fluid (CSF) inflammatory biomarkers were assessed with OLINK multiplex technology.

RESULTS

Proximity to, or exceeding, expected age of onset was associated with a sleep profile suggestive of hypersomnia (longer sleep and later morning awakening time). This hypersomnia sleep profile was associated with higher CSF neuroinflammatory biomarkers (IL-6, MCP-1, and global score). Interaction analyses revealed that some of these sleep-neuroinflammation associations were present mostly in those closer/exceeding the age of expected AD onset, APOE4 carriers, and those with better memory performance.

CONCLUSIONS

Proximity to, or exceeding, parental AD dementia onset was associated with a longer sleep pattern, which was related to elevated proinflammatory CSF biomarkers. We speculate that longer sleep may serve a compensatory purpose potentially triggered by neuroinflammation as individuals are approaching AD onset. Further studies should investigate whether neuroinflammatory-triggered long sleep duration could mitigate cognitive deficits.

Statin use moderates APOE's and CRP's associations with dementia and is associated with lesser dementia severity in ε4 carriers

INTRODUCTION

We tested the effect of statins on C-reactive protein (CRP) and apolipoprotein E (APOE)'s associations with dementia severity.

METHODS

A total of 1725 participants of the Alzheimer's Disease Neuroimaging Initiative (ADNI) were assigned from 12-month follow-up data into the following groups: (1) ε4 (-)/statin (-), (2) ε4 (-)/statin (+), (3) ε4 (+)/statin (-), and (4) ε4 (+)/statin (+). Dementia severity was assessed by a δ homolog: "dHABS." A mediation model was stratified on statin use and moderation effects tested by a chi-square difference.

RESULTS

Plasma CRP level decreased with ε4 allelic dose. Statins had no effect on the dHABS d-score in non-carriers but were associated with better scores in carriers. Treated carriers did not have more severe dementia than non-carriers. Statin use moderated the mutual adjusted effects of APOE and CRP. CRP was not a mediator of APOE's effect.

DISCUSSION

Statins may provide a protective effect on the dementia severity of ε4 carriers.

HIGHLIGHTS

δ is a dementia-specific phenotype related to general intelligence "g" and is assessed via a "d-score." Apolipoprotein E (APOE) and plasma C-reactive protein (CRP) are independently associated with δ. Plasma CRP decreases with ε4 allelic dose. Statins were associated with better (less demented) d-scores in ε4 carriers but had no effect in non-ε4 carriers. Treated ε4 carriers did not have more severe dementia than non-carriers. Statin use moderated the effects of APOE and CRP on δ. CRP was not a mediator of APOE's effect on δ.

The inverse association between the apolipoprotein E ε4 allele and C-reactive protein levels is stronger in persons with obesity and diabetes

BACKGROUND

C-reactive protein (CRP) is lower in patients who carry the apolipoprotein E epsilon 4 allele variant (APOEε4) of the APOE gene. This could however be explained by other factors observed in APOEε4 carriers, such as lower body mass index (BMI), possibly less diabetes and more use of statins, all associated with CRP concentrations.

OBJECTIVES

To assess the association between CRP and APOEε4 stratified by BMI, statin use and diabetes.

METHODS

We included 2700 community-dwelling older adults from the Hordaland health study with genotyping of the APOE gene by a one-step polymerase chain reaction and CRP measured using immuno-MALDI-TOF MS. Differences in CRP concentrations by APOE (ε4 vs no ε4) were assessed using the Mann-Whitney U tests, also stratified by statin use, diabetes and BMI categories. Finally, we performed linear regression with log (CRP) as the outcome and APOEε4 together with statin use, diabetes, BMI and their respective interactions.

RESULTS

CRP was higher in APOEε4 carriers irrespective of BMI, diabetes and statin use. In APOEε4 non-carriers, CRP was elevated with diabetes and obesity as expected. However, this was attenuated or even reversed in APOEε4 carriers. Such differences were not observed for statin use.

CONCLUSIONS

Statin use, obesity or diabetes did not confound the known association between the APOEε4 allele and lower CRP. Our data suggest that CRP is less responsive to inflammatory cues involved in diabetes and obesity in APOEε4 carriers. Epidemiological studies should take note of these relationships, as CRP, APOEε4, diabetes and obesity are both linked to neurodegenerative and cardiovascular disease.

Alteration of Blood Immune Biomarkers in MCI Patients with Different APOE Genotypes after Cognitive Training: A 1 Year Follow-Up Cohort Study

Many studies aim to detect the early phase of dementia. One of the major ways to achieve this is to identify corresponding biomarkers, particularly immune blood biomarkers. The objective of this study was to identify such biomarkers in patients with mild cognitive impairment (MCI) in an experiment that included cognitive training. A group of patients with MCI diagnoses over the age of 65 participated in the study (n = 136). Measurements of cognitive functions (using the Mini-Mental State Examination scale and Montreal Cognitive Assessment) and determination of 27 serum biomarkers were performed twice: on the first visit and on the second visit, one year after the cognitive training. APOE genotypes were also determined. Concentrations of EGF (F = 17; p = 0.00007), Eotaxin (F = 7.17; p = 0.008), GRO (F = 13.42; p = 0.0004), IL-8 (F = 8.16; p = 0.005), MCP-1 (F = 13.46; p = 0.0001) and MDC (F = 5.93; p = 0.016) increased after the cognitive training in MCI patients. All these parameters except IL-8 demonstrated a weak correlation with other immune parameters and were poorly represented in the principal component analysis. Differences in concentrations of IP-10, FGF-2, TGFa and VEGF in patients with MCI were associated with APOE genotype. Therefore, the study identified several immune blood biomarkers that could potentially be associated with changes in cognitive function.

Limited evidence of a shared genetic relationship between C-reactive protein levels and cognitive function in older UK adults of European ancestry

Introduction

Previous studies have shown associations between cognitive function and C-reactive protein (CRP) levels in older adults. Few studies have considered the extent to which a genetic predisposition for higher CRP levels contributes to this association.

Methods

Data was analyzed from 7,817 UK participants aged >50 years as part of the PROTECT study, within which adults without dementia completed a comprehensive neuropsychological battery. We constructed a polygenic risk score (PRS-CRP) that explained 9.61% of the variance in serum CRP levels (p = 2.362 × 10-7) in an independent cohort. Regressions were used to explore the relationship between PRS-CRP and cognitive outcomes.

Results

We found no significant associations between PRS-CRP and any cognitive measures in the sample overall. In older participants (>62 years), we observed a significant positive association between PRS-CRP and self-ordered search score (i.e., spatial working memory).

Conclusion

Whilst our results indicate a weak positive relationship between PRS-CRP and spatial working memory that is specific to older adults, overall, there appears to be no strong effects of PRS-CRP on cognitive function.

Impact of hs-CRP concentration on brain structure alterations and cognitive trajectory in Alzheimer's disease

Introduction

Present study was to investigate hs-CRP concentration, brain structural alterations, and cognitive function in the context of AD [Subjective cognitive decline (SCD), mild cognitive impairment (MCI), and AD].

Methods

We retrospectively included 313 patients (Mean age = 76.40 years, 59 SCD, 101 MCI, 153 AD) in a cross-sectional analysis and 91 patients (Mean age = 75.83 years, 12 SCD, 43 MCI, 36 AD) in a longitudinal analysis. Multivariable linear regression was conducted to investigate the relationship between hs-CRP concentration and brain structural alterations, and cognitive function, respectively.

Results

Hs-CRP was positively associated with gray matter volume in the left fusiform (β = 0.16, pFDR = 0.023) and the left parahippocampal gyrus (β = 0.16, pFDR = 0.029). Post hoc analysis revealed that these associations were mainly driven by patients with MCI and AD. The interaction of diagnosis and CRP was significantly associated with annual cognitive changes (β = 0.43, p = 0.008). Among these patients with AD, lower baseline CRP was correlated with greater future cognitive decline (r = -0.41, p = 0.013).

Conclusion

Our study suggests that increased hs-CRP level may exert protective effect on brain structure alterations and future cognitive changes among patients already with cognitive impairment.

High-Sensitivity C-Reactive Protein, Its Change, and Cognitive Function: A National Population-Based Cohort Study

This study aimed to evaluate the associations of baseline high-sensitivity C-reactive protein (Hs-CRP) and its change with subsequent cognitive decline and cognitive impairment. Data for this study were obtained from the China Health and Retirement Longitudinal Study, a national community-based prospective cohort study. Hs-CRP level and cognitive function were measured repeatedly over a 7-year follow-up. Linear mixed models and cox proportional hazard models were used to evaluate the associations. The study comprised 7385 participants (50.67% women, mean age 59.08 ± 8.86 years) with baseline Hs-CRP ranging from 0.03 to 178.10 mg/L (median: 1.01 mg/L, IQR: 0.55-2.11 mg/L). During a median of 5.79 years follow-up, the highest quartile of the Hs-CRP group showed a faster rate of cognitive decline (-0.0053 SD/year, p = 0.006) and a higher risk of cognitive impairment (HR 1.0814, p = 0.044) than those in the lowest quartile. Individuals in the elevated group of Hs-CRP change had a significantly faster cognitive decline (-0.0070 SD/year, p = 0.016) compared with those in the stable group. In this study, significant longitudinal associations between baseline Hs-CRP, elevated Hs-CRP, and long-term cognitive deterioration were observed. Hs-CRP level could perhaps serve as a predictor for cognitive deterioration in middle-aged and older adults.

The Association Between Diabetes Duration and Domain-Specific Cognitive Impairment: A Population-Based Study

BACKGROUND

Diabetes is a risk factor for cognitive impairment, and disease duration is associated with geriatric decline and functional disabilities.

OBJECTIVE

This study aimed to examine the association of diabetes duration with domain-specific cognitive impairment in elderly.

METHODS

A total of 3,142 participants from the National Health and Nutrition Examination Survey (NHANES) from the period between 2011 and 2014 were included. We assessed cognitive function using the Digit Symbol Substitution Test (DSST), the CERAD Word Learning (CERAD-WL) test, the CERAD Delayed Recall (CERAD-DR) test and animal fluency (AF) test.

RESULTS

After adjusting for age, sex, race/ethnicity, education level, and annual household income, we found that diabetes with a duration longer than 20 years were at 3.32-fold increased risk of DSST impairment (OR = 3.32, 95% CI: 1.95 to 5.67), 1.72-fold increased risk of CERAD-WL impairment (OR = 1.72, 95% CI: 1.13 to 2.62), and 1.76-fold increased risk of AF impairment (OR = 1.76, 95% CI: 1.23 to 2.53), compared with those with no diabetes. Associations were generally stronger in women than in men. Participants with diabetes, who were diagnosed at 50-59 years old were at increased risk of DSST impairment, CERAD-WL impairment, CERAD-DR impairment, and AF impairment per 5 years longer duration of diabetes.

CONCLUSION

Longer diabetes duration was associated with the increased risk of cognitive impairment, especially in processing speed and attention. The presence of chronic kidney disease was associated with the increased risk of DSST impairment.

Predictors of cognitive decline in older individuals without dementia: An updated meta-analysis

OBJECTIVE

To evaluate the effect of overall peripheral inflammatory levels on cognitive function, we explored the relationship between established biomarkers of peripheral inflammation (circulating C-reactive protein [CRP], interleukin-6 [IL-6], and tumor necrosis factor-α [TNF-α]) and cognitive decline by performing a review of observational studies and creating an updated summary.

METHODS

We included literatures exploring the relationship between peripheral levels of CRP, IL-6, and TNF-α and subsequent cognitive decline, published until July 2022, by searching the following databases: PubMed, Embase, Web of Science, the Cochrane Library, ClinicalTrials, CNKI, and VIP databases. We used random-effects models to pool the odds ratios (ORs) for the risks of subsequent cognitive decline in older adults with high levels of peripheral inflammation. We initially screened out 501 literatures, of which only 17 were ultimately eligible. Overall, there were 19,516 older individuals included in our meta-analysis, and 2134 of them experienced subsequent cognitive change.

RESULTS

Individuals with high levels of peripheral inflammation may have 14% more chance to develop subsequent cognitive decline than those with low levels (OR = 1.14, 95% CI: 1.03-1.27; p < 0.00001). In the subgroup analysis, the incidence of cognitive decline was higher in individuals with high levels of IL-6. This study further demonstrates the link between systemic inflammation and cognitive status.

INTERPRETATION

Detecting CRP, IL-6, and TNF-α in peripheral blood is necessary, as they may become effective indicators for forthcoming cognitive performance.

Boswellic Acids Improve Clinical Cognitive Scores and Reduce Systemic Inflammation in Patients with Mild to Moderate Alzheimer's Disease

BACKGROUND

Recent therapeutic approaches for Alzheimer's disease (AD) have had limited success. Considering the association of neuroinflammation with AD symptoms as demonstrated in multiple studies, assessment of the clinical efficacy of molecules that reduce systemic or brain inflammation is warranted.

OBJECTIVE

This clinical trial assessed whether boswellic acids can improve cognitive and neuropsychiatric symptoms while reducing inflammation in AD patients.

METHODS

A double-blind, placebo-controlled, study was conducted on 85 AD patients randomized to boswellic acids (K-Vie™ as the main ingredient in Memowell™) or placebo for 6 months. Clinical Dementia Rating-Sum of Boxes (CDR-SOB) and Mini-Mental State Examination (MMSE) scores were compared to baseline and between groups and constituted the co-primary clinical efficacy endpoints. Secondary outcomes included neuropsychiatric assessment (Neuropsychiatric Inventory-Questionnaire, NPI-Q) and assessment of AD and inflammation biomarkers.

RESULTS

Patients on K-Vie™ showed a 3.1- and 1.6-unit improvement in MMSE and CDR-SOB scores, respectively, when compared to patients on placebo. NPI-Q analysis revealed significant improvement in the K-Vie™ but not in the placebo group. Only mild gastrointestinal side effects were reported in a few patients. Patients on K-Vie™ showed improvement in plasma AD biomarkers and reduction of key inflammatory cytokines including IL-6 and TNF.

CONCLUSION

Our results support the positive cognitive effects of boswellic acids by reducing the systemic inflammation.

Peripheral high levels of CRP predict progression from normal cognition to dementia: A systematic review and meta-analysis

OBJECTIVE

Several cross-sectional studies have demonstrated a relationship between inflammation and dementia. Uncertainty exists over the ability of C-reactive protein (CRP), one of the most investigated markers of inflammation, to predict the progression of normal cognition to dementia. A systematic review and meta-analysis were performed to assess whether high peripheral levels of CRP are associated with cognitive impairment and whether CRP is a risk factor for predicting progression from normal cognition to cognitive decline or dementia.

METHODS

Literature published before November 2022 was retrieved from PubMed, Embase, and Web of Science. Prospective cohort studies that employed recognized evaluation instruments to assess global cognitive function or used accepted diagnostic criteria to ascertain dementia were selected. Subgroup analysis was conducted on specific cognitive domains and causes of dementia (i.e., Alzheimer's disease and vascular dementia). Odds ratios (ORs) and hazard ratios (HRs) were extracted and merged to facilitate data analysis. A random-effects model was used for the meta-analysis and a descriptive analysis of the data that could not be merged was conducted.

RESULTS

A total of 13 articles (14 cohort studies) were included for meta-analysis and six articles were included for descriptive analysis. The results showed that high CRP levels were not related to future cognitive decline (OR = 1.115; 95 % CI: 0.830-1.497; p = 0.469) but were associated with an increased risk of conversion to dementia. (HR = 1.473; 95 % CI: 1.037-2.090; p = 0.0394). This association persisted after full adjustment for potential covariates, with an OR of 1.044 (95 % CI:0.767-1.421, p = 0.785) for cognitive decline and an HR of 1.429 (95 % CI:1.088-1.876, p = 0.010) for dementia. The subgroup analysis showed that a higher level of CRP was related to a decline in visual-spatial ability (OR = 1.402, 95 % CI: 1.045-1.882, p = 0.024) and the risk of conversion to vascular dementia (total effect size of OR and HR = 2.769, 95 % CI: 1.586-4.83, p = 0.000).

CONCLUSIONS

Higher CRP levels as an indicator of chronic systemic inflammation cannot predict future cognitive decline but may indicate a higher risk of conversion to dementia.

Longitudinal associations between C-reactive protein and cognitive performance in normative cognitive ageing and dementia

BACKGROUND

systemic inflammation appears to play an important role in the pathogenesis and expression of Alzheimer's disease and other dementias. Previous research has found that elevated levels of serum C-reactive protein (CRP) is associated with poorer cognitive functioning and increased risk for dementia. However, most studies are limited by single CRP measurements, which fail to capture long-term inflammatory exposures or dynamic changes in inflammation and cognition which may occur across repeated measurements.

METHODS

using data from 3,563 older adults aged 65-101 from the Health and Retirement Study, we examined bivariate changes in CRP and cognition measured repeatedly over a 10-year follow-up. Bivariate multilevel models estimated the effect of time-varying CRP on cognition among cognitively healthy older adults and in a subset of 427 participants who reported incident dementia onset during the follow-up period.

RESULTS

in cognitively healthy participants, CRP was associated with lower level of cognitive functioning, but not rate of change over time. This effect was significant in participants under 80 years of age (b = -0.09, standard error (SE) = 0.05, P = 0.04), but not in older participants. In participants with incident dementia, those with higher CRP experienced smaller rates of cognitive decline, leading up to dementia diagnosis.

CONCLUSIONS

elevated levels of CRP predict poorer cognition and increased dementia risk in cognitively healthy adults under the age of 80. Conversely, increased CRP may confer protective effects on cognition in the prodromal stage of dementia.

Immune function, cortisol, and cognitive decline & dementia in an aging latino population

BACKGROUND

The etiology of dementias and cognitive decline remain largely unknown. It is widely accepted that inflammation in the central nervous system plays a critical role in the pathogenesis of dementia. However, less is known about the role of the peripheral immune system and interactions with cortisol, though evidence suggests that these, too, may play a role.

METHODS

Using data from 1337 participants aged 60+ years from the Sacramento Area Latino Study of Aging (observational cohort) we investigated variation in trajectories of cognitive decline by pathogen IgG and cytokine levels. Linear mixed effects models were used to examine the association between baseline Interleukin (IL)-6, C-reactive protein, tumor necrosis factor (TNF)-α, and five persistent pathogens' IgG response and trajectories of cognition over 10 years, and to examine interactions between immune biomarkers and cortisol. Stratified cumulative incidence functions were used to assess the relation between biomarkers and incident dementia. Inverse probability weights accounted for loss-to-follow-up and confounding.

RESULTS

IL-6, TNF-α, and CMV IgG were statistically significantly associated with a higher log of Modified Mini-Mental State Examination errors (IL-6, β=0.0935 (95%CI: 0.055, 0.13), TNF-alpha β= 0.0944 (95%CI: 0.032, 0.157), and CMV, β= 0.0409 (95%CI: 0.013, 0.069)). Furthermore, cortisol interacted with HSV-1 and IL-6, and CRP for both cross-sectional cognitive function and rate of decline. No statistically significant relationship was detected between biomarkers and incidence of dementia.

CONCLUSIONS

These findings support the theory that the peripheral immune system may play a role in cognitive decline but not incident dementia. Furthermore, they identify specific markers amenable for intervention for slowing decline.

Mediterranean Diet and Risk of Dementia and Alzheimer's Disease in the EPIC-Spain Dementia Cohort Study

The Mediterranean diet (MD) has shown to reduce the occurrence of several chronic diseases. To evaluate its potential protective role on dementia incidence we studied 16,160 healthy participants from the European Prospective Investigation into Cancer and Nutrition (EPIC)-Spain Dementia Cohort study recruited between 1992-1996 and followed up for a mean (±SD) of 21.6 (±3.4) years. A total of 459 incident cases of dementia were ascertained through expert revision of medical records. Data on habitual diet was collected through a validated diet history method to assess adherence to the relative Mediterranean Diet (rMED) score. Hazard ratios (HR) of dementia by rMED levels (low, medium and high adherence levels: ≤6, 7-10 and ≥11 points, respectively) were estimated using multivariable Cox models, whereas time-dependent effects were evaluated using flexible parametric Royston-Parmar (RP) models. Results of the fully adjusted model showed that high versus low adherence to the categorical rMED score was associated with a 20% (HR = 0.80, 95%CI: 0.60-1.06) lower risk of dementia overall and HR of dementia was 8% (HR = 0.92, 0.85-0.99, p = 0.021) lower for each 2-point increment of the continuous rMED score. By sub-types, a favorable association was also found in women for non-AD (HR per 2-points = 0.74, 95%CI: 0.62-0.89), while not statistically significant in men for AD (HR per 2-points = 0.88, 0.76-1.01). The association was stronger in participants with lower education. In conclusion, in this large prospective cohort study MD was inversely associated with dementia incidence after accounting for major cardiovascular risk factors. The results differed by dementia sub-type, sex, and education but there was no significant evidence of effect modification.

Systemic inflammation as a moderator between sleep and incident dementia

STUDY OBJECTIVES

To determine whether C-reactive protein (CRP), a marker of systemic inflammation, moderates the association between sleep and incident dementia.

METHODS

We studied Framingham Heart Study participants who completed at baseline a serum CRP assessment and in-home polysomnography to measure sleep duration, sleep efficiency, sleep latency, wake after sleep onset (WASO), number of awakenings, arousal index, and apnea-hypopnea index. Participants were divided into groups according to their CRP level: low (<1 mg/L), average (1-3 mg/L), and high inflammation (>3 mg/L). Surveillance for outcomes (incident all-cause and Alzheimer's disease [AD] dementia) commenced at baseline and continued up to 22.5 years.

RESULTS

In 291 participants (mean age 67.5 ± 4.9 years, 51.6% men) followed for 13.4 ± 5.4 years, we observed 43 cases of all-cause dementia, 33 of which were clinically consistent with AD. Whereas no direct association between CRP or sleep exposures was observed with incident dementia, CRP levels interacted with nighttime wakefulness when predicting both incident all-cause and AD dementia. In the high CRP group, longer WASO (hazard ratio [HR], 2.89; 95% CI, 1.31-6.34) and more nighttime awakenings (HR, 4.55; 95% CI, 1.19-17.38) were associated with higher risk of incident dementia. In the low CRP group, fewer nighttime awakenings were associated with a higher risk of incident dementia (HR, 0.07; 95% CI, 0.01-0.68).

CONCLUSIONS

Our findings suggest that inflammation moderates the association between sleep, particularly nighttime wakefulness, and dementia risk. The presence of inflammation may be an important determinant in evaluating how sleep disturbances relate to neurodegeneration.

APOE - a genetic marker of comorbidity in subjects with morbid obesity

Background

In population-based studies, the genetic variability of the APOE E alleles have been associated with health outcomes. Health problems are common in subjects with obesity. This study explored associations between the APOE E alleles and comorbidity in subjects with morbid obesity.

Methods

The study included consecutive subjects referred for evaluation of bariatric surgery with morbid obesity (defined as BMI > 40 or > 35 kg/m² with complications related to obesity). The subjects followed a conservative weight loss program for 6 months before surgery and had a follow-up visit 12 months after surgery. Demographic data and a set psychosomatic scores (musculoskeletal pain, WHO-5 Well-Being Index, Rosenberg Self-Esteem Scale, Hopkins Symptom Check-list 10; Epworth Sleepiness Scale, and Fatigue Severity Scale) were collected, and blood samples were analysed for haematological and biochemical parameters and APOE alleles.

Results

One hundred and forty subjects (men/women: 32 (23%)/108 (77%) with mean age 43.0 (SD 8.7) years and BMI 42.1 (SD 3.8) kg/m² were included. One hundred and eight and 92 subjects had data after conservative treatment and 12 months after surgery, respectively. The prevalence of the APOE alleles were: E2E2: 1 (0.7%), E2E3: 13 (9.3%), E2E4: 4 (2.9%), E3E3: 71 (50.7%), E3E4: 47 (33.6%), and E4E4: 4 (2.9%). The prevalence rates were as anticipated in a Norwegian population. The weight loss during conservative treatment and after bariatric surgery was independent of E allele variability. E2 was associated with a significant or clear trend toward improvement of all psychosomatic disorders. There was a significant fall in CRP during the two treatment periods with weight loss. E2 and E4 were significantly associated with high and low CRP, respectively, but no associations were seen between CRP and comorbidity.

Conclusions

The most marked finding was the association between E2 and improvement of all psychosomatic disorders. The positive and negative associations between CRP and E2 and E4, respectively, could indicate effects on inflammation and immunological reactions.

Apolipoprotein E genotype and the association between C-reactive protein and postoperative delirium: Importance of gene-protein interactions

INTRODUCTION

Apolipoprotein E (APOE) status may modify the risk of postoperative delirium conferred by inflammation.

METHODS

We tested whether APOE modifies the established association between C-reactive protein (CRP) and delirium incidence, severity, and duration in 553 noncardiac surgical patients aged 70 and older. High postoperative plasma CRP (≥234.12 mg/L) was defined by the highest sample-based quartile. Delirium was determined using the Confusion Assessment Method and chart review, and severity was determined by the Confusion Assessment Method-Severity score.

RESULTS

APOE ε4 carrier prevalence was 19%, and postoperative delirium occurred in 24%. The relationship between CRP and delirium incidence, severity, and duration differed by ε4 status. Among ε4 carriers, there was a strong relationship between high CRP (vs. low CRP) and delirium incidence (relative risk [95% confidence interval], 3.0 [1.4-6.7]); however, no significant association was observed among non-ε4 carriers (relative risk [95% CI], 1.2 [0.8-1.7]).

DISCUSSION

Our findings raise the possibility that APOE ε4 carrier status may modify the relationship between postoperative day 2 CRP levels and postoperative delirium.

Associations of hemoglobin A1c with cognition reduced for long diabetes duration

Introduction

Associations of some risk factors with poor cognition, identified prior to age 75, are reduced or reversed in very old age. The Protected Survivor Model predicts this interaction due to enhanced survival of those with extended risk factor duration. In a younger sample, this study examines the association of cognition with the mean hemoglobin A1c risk factor over the time at risk, according to its duration.

Methods

The interaction of mean hemoglobin A1c (average = 9.8%), evaluated over duration (average = 116.8 months), was examined for overall cognition and three cognitive domains in a sample of 150 “young-old” veterans (mean age = 70) with type 2 diabetes.

Results

The predicted interactions were significant for overall cognition and attention, but not executive functions/language and memory.

Discussion

Findings extend the Protected Survivor Model to a “young-old” sample, from the very old. This model suggests focusing on individuals with good cognition despite prolonged high risk when seeking protective factors.

Inflammation: Bridging Age, Menopause and APOEε4 Genotype to Alzheimer's Disease

Neuro-inflammatory processes that contribute to development of Alzheimer’s are evident early in the latent prodromal phase and worsen during the course of the disease. Despite substantial mechanistic and clinical evidence of inflammation, therapeutic approaches targeting inflammation have failed to alter the course of the disease. Disparate results from epidemiological and clinical trials targeting inflammation, highlight the complexity of the inflammatory process. Herein we review the dynamics of the inflammatory process across aging, midlife endocrine transitions, and the APOEε4 genotype and their contribution to progression of Alzheimer’s disease (AD). We discuss the chronic inflammatory processes that are activated during midlife chronological and endocrine aging, which ultimately limit the clearance capacity of microglia and lead to immune senescence. Aging, menopause, and APOEε4 combine the three hits of a compromised bioenergetic system of menopause with the chronic low grade innate inflammation of aging with the APOEε4 dyslipidemia and adaptive immune response. The inflammatory immune response is the unifying factor that bridges across each of the risk factors for AD. Immune system regulators that are specific to stage of disease and inflammatory phenotype would provide a therapeutic strategy to disconnect the bridge that drives disease. Outcomes of this analysis provide plausible mechanisms underlying failed clinical trials of anti-inflammatory agents in Alzheimer’s patients. Further, they highlight the need for stratifying AD clinical trial cohorts based on inflammatory phenotype. Combination therapies that include targeted use of anti-inflammatory agent’s specific to the immune phenotype are considered.

Systemic Inflammation Is Associated With Longitudinal Changes in Cognitive Performance Among Urban Adults

Objectives/Background: Systemic inflammation can affect cognitive performance over time. The current study examined associations between systemic inflammation and cognitive performance among African Americans and Whites urban adults, stratifying by sex, and age group and by race. Patients/Methods: Among 1,555-1,719 White and African-American urban adults [Age_base: 30-64y, 2004-2013, mean±SD follow-up time(y): 4.64 ± 0.93y], conducted linear mixed-effects regression models were conducted to test associations of inflammatory markers [C-reactive protein, Erythrocyte Sedimentation Rate (ESR), albumin, iron, and an inflammation composite score (ICS)] with longitudinal cognitive performance. Results: Among key findings, CRP was linked to poorer baseline mental status among younger women (≤50y, γ₀₁ = -0.03 ± 0.01, p = 0.002) and poorer attention in older women (>50y, γ₀₁ = -0.024 ± 0.007, p < 0.004) and African-Americans (γ₀₁ = -0.029 ± 0.008, p < 0.001). ESR was related to faster decline on verbal memory among older men (>50y, γ₁₁ = -0.008 ± 0.003, P = 0.009); with poorer performance on attention tests overall (γ₀₁ = -0.010 ± 0.003, P = 0.003) and among African-Americans (γ₀₁ = -0.013 ± 0.004, P = 0.002); on verbal fluency among older women (>50y,γ₀₁ = -0.037 ± 0.013, P = 0.004) and on executive function: overall (γ₀₁ = +0.62 ± 0.21, P = 0.004), older men (>50y, γ₀₁ = +1.69 ± 0.53, P = 0.001) and African-Americans (γ₀₁ = +0.84 ± 0.28, P = 0.002). Albumin was linked to slower attention decline among older men (>50y, γ₁₁ = +0.329 ± 0.103, P = 0.009), over-time improvement in executive function overall (γ₁₁ = -6.00 ± 2.26, P = 0.008), and better baseline psychomotor speed among African-Americans (γ₀₁ = +0.56 ± 0.19, P = 0.003). Finally, ICS predicted faster decline on visual memory/visuo-constructive abilities among older men (>50y, γ₁₁ = +0.17 ± 0.06, p = 0.003). Conclusion: In sum, strong associations between systemic inflammation and longitudinal cognitive performance were detected, largely among older individuals (>50y) and African-Americans. Randomized trials targeting inflammation are warranted.

Chronically raised C-reactive protein is inversely associated with cortical β-amyloid in older adults with subjective memory complaints

BACKGROUND

Inflammation promotes amyloidogenesis in animals and markers of inflammation are associated with β-amyloid (Aβ) in humans. Hence, we sought to examine the cross-sectional associations between chronically elevated plasma C reactive protein (CRP) and cortical Aβ in 259 non-demented elderly individuals reporting subjective memory complaints from the Multidomain Alzheimer Preventive Trial (MAPT).

METHODS

Cortical-to-cerebellar standard uptake value ratios were obtained using [¹⁸F] florbetapir positron emission tomography (PET). CRP was measured in plasma using immunoturbidity. Chronically raised CRP was defined as having 2 consecutively high CRP readings (>3 mg/l ≤ 10 mg/l) between study baseline and the 1 year visit (visits were performed at baseline, 6 months, 1 year and then annually). Associations were explored using adjusted multiple linear regression.

RESULTS

Chronically raised CRP was found to be inversely associated with cortical Aβ (B-coefficient: -0.054, SE: 0.026, p = 0.040) and this association seemed to be specific to apolipoprotein E (Apo E) ε4 carriers (B-coefficient: -0.130, SE: 0.058, p = 0.027). CRP as an isolated reading measured closest to PET scan was also inversely associated with cortical Aβ when CRP was treated as a dichotomized variable (high CRP > 3 mg/l ≤ 10 mg/l, B-coefficient: -0.048, SE: 0.023, p = 0.043).

CONCLUSIONS

Our preliminary findings suggest that inflammation might be beneficial in the early stages of Alzheimer's disease as the immune systems attempts to combat Aβ pathology particularly in ApoE ε4 carriers. Investigating the temporal relationships between cerebral Aβ and a panel of inflammatory markers would provide further evidence as to whether chronic inflammation might modulate amyloidogenesis in vivo.

The protected survivor model: Using resistant successful cognitive aging to identify protection in the very old

For some cardiovascular risk factors, association with risk for cognitive impairment observed in early old age is reduced, or paradoxically even reversed, as age of outcome increases. Successful cognitive aging is intact cognition in the oldest-old; we define resistant successful cognitive aging as successful cognitive aging despite high risk. The protected survivor model posits that a minority of the general population has a protective factor that mitigates the negative effect of a risk factor on successful cognitive aging for the unprotected majority. As age increases, differential failure rates increase the proportion of survivors with protection. Among the unprotected, the proportion with low risk increases, but among those with protection, high risk and low risk do not differ. Due to differential mortality, half the survivors are eventually protected - a majority among those with high risk, and a minority among those with low risk. According to the protective survivor model, an example of Simpson's paradox, the association of the risk factor with survival does not change within an individual, but the association in the surviving population changes as its age increases. We created quantitative illustrations of a simplified protected survivor model applied to successful cognitive aging to explain how the usual association of a risk factor with cognitive decline is reversed in the very old. In the illustrations, probability of subsequent survival was higher for survivors with high risk (mostly protected) than low risk (mostly not protected), an example of Simpson's paradox. Resistance to disease despite the presence of risk factors is consistent with the presence of countervailing protection. Based on the protected survivor model, we hypothesize that studies seeking protective factors against cognitive decline will be more effective by limiting a successful cognitive aging sample to resistant successful cognitive aging - to contrast with a sample without successful cognitive aging.

Peripheral Inflammatory Biomarkers and Cognitive Decline in Older Adults With and Without Alzheimer's Disease: A Systematic Review

Peripheral inflammatory biomarkers may play an important role in the cognitive decline of aging and incidence of Alzheimer's disease (AD); however, data from epidemiological studies present conflicting findings. The purpose of the current review was to systematically determine the current state of the science on the association between peripheral inflammatory biomarkers and cognitive decline. Articles published from January 1, 2006 to October 28, 2016 were searched using the Medline and Embase databases. Nine studies met inclusion criteria (two examined participants with AD dementia and seven examined participants without dementia). Although a wide range of peripheral inflammatory biomarkers was examined, C-reactive protein and interleukin 6 were the most studied. Findings show conflicting results for the association between peripheral inflammatory biomarkers and cognitive decline. Peripheral inflammation may harm and help the brain, and therefore, the challenge of modulating immunity will be to find ways of fine tuning inflammation to delay, prevent, or treat AD. [Journal of Gerontological Nursing, 43(12), 53-60.].

Few serum proteins mediate APOE's association with dementia

The latent variable "δ" (for "dementia") appears to be uniquely responsible for the dementing aspects of cognitive impairment. Age, depression, gender and the apolipoprotein E (APOE) e4 allele are independently associated with δ. In this analysis, we explore serum proteins as potential mediators of APOE's specific association with δ in a large, ethnically diverse longitudinal cohort, the Texas Alzheimer's Research and Care Consortium (TARCC). APOE was associated only with C-Reactive Protein (CRP), Adiponectin (APN) and Amphiregulin (AREG), although the latter two's associations did not survive Bonferroni correction for multiple comparisons. All three proteins were associated with δ and had weak potential mediation effects on APOE's association with that construct. Our findings suggest that APOE's association with cognitive performance is specific to δ and partially mediated by serum inflammatory proteins. The majority of APOE's significant unadjusted effect on δ is unexplained. It may instead arise from direct central nervous system effects, possibly on native intelligence. If so, then APOE may exert a life-long influence over δ and therefore all-cause dementia risk.

Interaction between C-reactive protein and cognitive functions according to APOE gene polymorphism in post-menopausal women

INTRODUCTION

A potential factor increasing the risk of the development of cognitive impairment with age is apolipoprotein E (APOE) ε4 carrier status. A subsequent factor which may increase the risk of development of cognitive impairment at an older age is the concentration of C-reactive protein (CRP). The objective of the study was to examine the relationship between cognitive functions and the concentration of CRP in post-menopausal women who were carriers of particular apolipoprotein E gene (APOE) polymorphisms.

MATERIAL AND METHODS

A group of 402 women was recruited to the study. The inclusion criteria were: minimum two years after the last menstruation, follicle-stimulating hormone (FSH) concentration 30 U/ml, no dementi signs on Montreal Cognitive Assessment (MoCA). The computerized battery of the Central Nervous System Vital Signs (CNS VS) test was used to diagnose cognitive functions. APOE genotyping was performed by multiplex PCR. The blood plasma CRP levels were determined. Statistical analysis was performed using Statistica software.

RESULTS

The level of neurocognitive index (NCI) and cognitive functions in post-menopausal women depends on apolipoprotein E gene polymorphism (p < 0.001) and the concentration of CRP (p < 0.05). A negative correlation was found between CRP and NCI (p = 0.018), and the reaction time (p = 0.008) of women with APOE ε2/ε3. A positive correlation was observed between CRP and visual memory (p = 0.025) in women with APOE ε3/ε3, and verbal memory (p = 0.023) in women with APOE ε3/ε4 or ε4/ε4.

CONCLUSIONS

Apolipoprotein E gene polymorphism may modify the relationship between CRP concentration and cognitive functions in post-menopausal women.

Elevated C-Reactive Protein Is Associated with Cognitive Decline in Outpatients of a General Hospital: The Project in Sado for Total Health (PROST)

BACKGROUND/AIMS

We aimed to determine whether the concentration of serum C-reactive protein (CRP) is associated with cognitive function in an adult Japanese population.

METHODS

Participants of this cross-sectional study were from a subgroup of the Project in Sado for Total Health (PROST; n = 454; mean age, 70.5 years). The cognitive state was evaluated using the Mini-Mental State Examination (MMSE), and those with an MMSE score <24 were considered 'cognitively declined'. Concentrations of serum high-sensitivity CRP were measured. Multiple logistic regression analysis was used to calculate odds ratios (ORs) for cognitive decline, adjusting for the covariates of age, sex, BMI, disease history, and APOE allele.

RESULTS

Of the 454 participants, 94 (20.7%) were cognitively declined. Relative to the lowest (first) quartile of CRP concentration, adjusted ORs were 1.29 (95% CI 0.61-2.75) for the second, 1.78 (95% CI 0.82-3.86) for the third, and 3.05 (95% CI 1.45-6.42) for the highest (fourth) quartiles (p for trend = 0.018). When data were stratified by sex, the association between CRP concentration and cognitive decline was observed only in women.

CONCLUSION

Our findings suggest an association between higher CRP concentration and lower cognitive function. Chronic inflammation may affect cognitive function in adults, in particular women.

Cognitive Ageing in Great Britain in the New Century: Cohort Differences in Episodic Memory

BACKGROUND

Dementias in high income countries are set to be the third major burden of disease even as older people are increasingly required to think for themselves how to provide for their lives in retirement. Meanwhile the period of older age continues to extend with increase in life expectancy. This challenge demands an understanding of how cognition changes over an extended period in later life. But studying cognitive ageing in the population faces a difficulty from the fact that older respondents are liable to leave (attrite) before study completion. This study tested three hypotheses: trajectories of cognitive ageing in Britain show an improvement beyond the age of 50; and they are lifted by secular improvement in cognition across cohorts; lastly they are susceptible to distortion due to attrition.

METHODS AND FINDINGS

Using the English Longitudinal Study of Ageing, this paper studied trajectories of episodic memory of Britons aged 50-89 from 2002 to 2013 (N = 5931). Using joint models the analysis found that levels of episodic memory follow a curvilinear shape, not a steady decline, in later life. The findings also revealed secular improvement in cognitive ageing such that as a cohort is being replaced episodic memory levels in the population improve. The analysis lastly demonstrated that failure to simultaneously model attrition can produce distorted pictures of cognitive ageing.

CONCLUSION

Old age in this century is not necessarily a period dominated by cognitive decline. In identifying behavioural factors associated with better cognitive ageing, such as social connections of traditional and online kinds, the paper raises possibilities of mustering an adequate response to the cognition challenge.

Repeated systemic inflammation was associated with cognitive deficits in older Britons

Introduction

The relationship of C-reactive protein (CRP) to cognition in the older old group (≥75 years) has recently been found positive on both sides of the Atlantic. We hypothesized that higher levels of CRP and fibrinogen are related to worse episodic memory throughout later life (≥50 years).

Methods

Data are drawn from older Britons free of dementias in the English Longitudinal Study of Aging 2004–2013. We applied growth trajectory models to repeated observations of episodic memory, CRP, and fibrinogen levels (and sociodemographic confounders). We accounted for practice effects in repeated tests of cognition.

Results

Higher levels of both inflammatory markers were associated with worse episodic memory, where a fibrinogen effect is evident throughout later life (coefficient −0.154; 95% confidence interval [CI] −0.254 to −0.054). Most importantly, the CRP effect is strongly negative among the older old group (coefficient −0.179; CI −0.320 to −0.038).

Discussion

Higher levels of fibrinogen are detrimental to older people's cognition, and among the older old, raised CRP levels are comparably deleterious. Repeated measures of inflammation can be considered in clinical practice as part of a response to the challenge of dementias.

Inflammatory markers and physical performance in middle-aged and older people in Indonesia

BACKGROUND

although recent studies have suggested that inflammation may play an important role in the process of ageing and in the development of disabilities, knowledge about the role of inflammation in physical performance decline among middle-aged and older people in the context of developing countries is limited.

OBJECTIVES

to examine the association between C-reactive protein (CRP) and the activities of daily living (ADL) among middle-aged (40-54 years old) and older (55-96 years old) people in Indonesia.

DATA

data from a population-based sample, the Indonesia Family Life Survey (IFLS) 2007, were analysed. The data consist of 1,702 respondents of middle age (40-54 years old) and 2,017 older respondents who had completed information on ADL and CRP.

METHODS

CRP concentrations in Dried Blood Spot (DBS) specimens were measured, using the validated enzyme-linked immunosorbent assay (ELISA) method. Thirteen items of ADL were used to measure physical performance. A three-level linear model was applied to take advantage of the nested structure of data at the individual level within the household and community levels.

RESULTS

high levels of CRP were significantly associated with lower ADL for middle-aged and older people (P < 0.001). The model was adjusted for co-morbid conditions, health risk factors, medications, depressive symptoms and sociodemographic characteristics.

CONCLUSION

the significant association between the high level of CRP and lower ADL among older people in Indonesia is in line with earlier studies in the context of developed countries. This study provides an extension in which the significant association was also found in middle-aged people (40-54 years old).

Low-grade inflammation differentiates between symptoms of apathy and depression in community-dwelling older individuals

BACKGROUND

Systemic low-grade inflammation has repeatedly been associated with depression in old age, but the relationship with apathy is less clear. The present study assessed whether C-reactive protein (CRP) is differentially associated with symptoms of apathy and depression.

METHODS

A population-based cohort study was carried-out. At baseline and after two and four years of follow-up, CRP levels were assessed and symptoms of apathy and depression were measured using the 15-item Geriatric Depression Scale. Logistic regression analysis was used to investigate the cross-sectional and longitudinal associations of CRP with symptoms of apathy and depression.

RESULTS

Two thousand forty-seven community-dwelling participants (70-78 years) without a history of cardiovascular disease or stroke were studied. A cross-sectional association was found between CRP and apathy symptoms at three time points (odds ratio (OR) per natural log unit increase in CRP: baseline visit = 1.40, 95% CI = 1.12-1.75; two-year follow-up visit = 1.62, 95% CI = 1.17-2.25; four-year follow-up visit = 1.51, 95% CI = 1.03-2.21). This did not change after adjustment for demographics and depressive symptoms, and was slightly attenuated after adjustment for cardiovascular risk factors. No cross-sectional association was found with depressive symptoms. Baseline CRP did not predict incident apathy or depressive symptoms during four years of follow-up.

CONCLUSIONS

Increased CRP levels are associated with apathy symptoms but not with depressive symptoms. This suggests a differential effect of inflammation on apathy and depression. In older persons, symptoms of apathy may be a behavioral manifestation of concurrent low-grade inflammation.

Longitudinal inflammation, cognitive decline, and Alzheimer's disease: a mini-review

The role of inflammation in cognitive decline has generated considerable interest, although few longitudinal evaluations have been conducted. A review of the literature yields mixed findings but suggests that inflammatory dysregulation is evident and may be related to clinical outcomes. The directionality, magnitude, and progression of these associations remain unclear. Future studies employing multiple time points of inflammatory data along with Alzheimer's disease (AD) biomarkers are critical for explication of longitudinal inflammation in cognitive decline.