The validity of dementia diagnoses in routinely collected electronic health records in the United Kingdom: A systematic review

Predictors of primary care psychological therapy outcomes for depression and anxiety in people living with dementia: evidence from national healthcare records in England

BACKGROUND

Psychological therapies can be effective in reducing symptoms of depression and anxiety in people living with dementia (PLWD). However, factors associated with better therapy outcomes in PLWD are currently unknown.

AIMS

To investigate whether dementia-specific and non-dementia-specific factors are associated with therapy outcomes in PLWD.

METHOD

National linked healthcare records were used to identify 1522 PLWD who attended psychological therapy services across England. Associations between various factors and therapy outcomes were explored.

RESULTS

People with frontotemporal dementia were more likely to experience reliable deterioration in depression/anxiety symptoms compared with people with vascular dementia (odds ratio 2.98, 95% CI 1.08-8.22; P = 0.03) or Alzheimer's disease (odds ratio 2.95, 95% CI 1.15-7.55; P = 0.03). Greater depression severity (reliable recovery: odds ratio 0.95, 95% CI 0.92-0.98, P < 0.001; reliable deterioration: odds ratio 1.73, 95% CI 1.04-2.90, P = 0.04), lower work and social functioning (recovery: odds ratio 0.98, 95% CI 0.96-0.99, P = 0.002), psychotropic medication use (recovery: odds ratio 0.67, 95% CI 0.51-0.90, P = 0.01), being of working age (recovery: odds ratio 2.03, 95% CI 1.10-3.73, P = 0.02) and fewer therapy sessions (recovery: odds ratio 1.12, 95% CI 1.09-1.16, P < 0.001) were associated with worse therapy outcomes in PLWD.

CONCLUSIONS

Dementia type was generally not associated with outcomes, whereas clinical factors were consistent with those identified for the general population. Additional support and adaptations may be required to improve therapy outcomes in PLWD, particularly in those who are younger and have more severe depression.

The association between atrial fibrillation and dementia: A UK linked electronic health records cohort study

BACKGROUND

We investigated the association between atrial fibrillation (AF) and dementia, and its subtypes (vascular-VaD, Alzheimer, mixed and rare dementia), and identified predictors for dementia in AF patients.

METHODS

The analysis was based on 183,610 patients with new-onset AF and 367,220 non-AF controls in the United Kingdom between 1998 and 2016, identified in three prospectively collected, linked electronic health records sources. Time-to-event (dementia or subtypes) analyses were performed using Cox proportional hazards and weighted Cox. Sub-analyses performed: including & censoring stroke and age (median used as cut-off).

RESULTS

Over a median follow-up of 2.67 years (IQR .65-6.02) for AF patients and 5.84 years for non-AF patients (IQR 2.26-11.80), incidence of dementia in the AF cohort was 2.65 per 100 person-years, compared to 2.02 in the non-AF cohort. After adjustment, a significant association was observed between AF and all-cause dementia (HR = 1.38, 95% CI: 1.31-1.45), driven by a strong association with VaD (HR = 1.55, 95% CI: 1.41-1.70). AF was also associated with mixed dementia (HR = 1.26, 95% CI: 1.01-1.56), but we could not confirm an association with Alzheimer (HR = 1.05, 95% CI: .94-1.16) and rare dementia forms (HR = 1.19, 95% CI: .90-1.56). Ischemic stroke (HR = 1.40, 95% CI: 1.26-1.56), subarachnoid haemorrhage (HR = 2.08, 95% CI: 1.47-2.96), intracerebral haemorrhage (HR = 1.95, 95% CI: 1.54-2.48) and diabetes (HR = 1.32, 95% CI: 1.24-1.41) were identified as the strongest predictors of dementia in AF patients.

CONCLUSIONS

AF patients have an increased risk of dementia, independent of stroke, with highest risk of VaD. Management and prevention of the identified risk factors could be crucial to reduce the increasing burden of dementia.

Statin Use and All-Cause Mortality in Nursing Home Residents With and Without Dementia: A Retrospective Cohort Study Using Claims Data

BACKGROUND AND OBJECTIVES

Little is known about the benefits of statin therapy in older adults with dementia. We aimed to evaluate the role of statin use for all-cause mortality in nursing home residents with and without dementia.

METHODS

This retrospective cohort study used claims data collected between January 2015 and December 2019 from a German health and long-term care insurance provider. Propensity score-based Cox proportional hazards models were used to evaluate the association of statin use with all-cause mortality and adjusted for potential confounders in nursing home residents. Subgroup analyses were performed based on the presence or absence of atherosclerotic cardiovascular disease (ASCVD), statin intensity (low, moderate, high), dementia type, age, sex, and level of care required.

RESULTS

A total of 282,693 participants were included in the study, of which 96,162 were matched. In total, 68.9% were women, and the mean age was 82.91 years (SD ±7.97). The average observation period was 2.25 years (SD ±1.35), and 54,269 deaths were recorded. Statin use in individuals with dementia resulted in lower all-cause mortality (hazard ratio [HR] 0.80, 95% CI 0.78-0.82, p < 0.001) compared with statin nonusers. Similarly, in individuals without dementia, statin use was associated with lower all-cause mortality (HR 0.73, 95% CI 0.71-0.76, p < 0.001) compared with statin nonusers. Similar findings were observed in subanalyses excluding participants with a history of ASCVD and across subgroups stratified by age, sex, care level required, and dementia type. Statin benefits were consistent among individuals with and without dementia.

DISCUSSION

Statin benefits were consistent among individuals with and without dementia. Statin therapy may be continued in nursing home residents with dementia to mitigate the risk of all-cause mortality.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that nursing home patients receiving statins have a lower mortality rate, whether they have a dementia diagnosis or not.

Phosphodiesterase Type 5 Inhibitors in Men With Erectile Dysfunction and the Risk of Alzheimer Disease: A Cohort Study

BACKGROUND AND OBJECTIVES

Repurposing phosphodiesterase type 5 inhibitors (PDE5Is) as drugs for Alzheimer disease (AD) risk reduction has shown promise based on animal studies. However, evidence in humans remains inconclusive. Therefore, we conducted a cohort study to evaluate the association between PDE5I initiation compared with nonuse and the risk of developing AD in men with erectile dysfunction (ED).

METHODS

Using electronic health records from IQVIA Medical Research Data UK (formerly known as the THIN database), we identified men aged ≥40 years with a new diagnosis of ED between 2000 and 2017. Individuals with a previous diagnosis of dementia, cognitive impairment, confusion, or prescription for dementia symptoms were excluded. The occurrence of incident AD was identified using diagnostic read codes. To minimize immortal-time bias, PDE5I initiation was treated as a time-varying exposure variable. Potential confounders were adjusted using inverse probability of treatment weighting based on propensity scores. Cox proportional hazard models were used to estimate the adjusted hazard ratio (HR) with 95% CIs. A secondary analysis explored the association between AD and the cumulative number of PDE5I prescriptions. Sensitivity analyses included lag (delay) periods of 1 and 3 years after cohort entry to address the prodromal stage of AD.

RESULTS

The study included 269,725 men, with 1,119 newly diagnosed with AD during a median follow-up of 5.1 (interquartile range 2.9-8.9) years. The adjusted HR in PDE5I initiators compared with nonuse was 0.82 (95% CI 0.72-0.93). The associated risk of AD decreased in individuals issued >20 prescriptions: HR 0.56 (95% CI 0.43-0.73) for 21-50 prescriptions and HR 0.65 (95% CI 0.49-0.87) for >50 prescriptions. Sensitivity analysis with a 1-year lag period supported the primary findings (HR 0.82, 95% CI 0.72-0.94), but the results differed with the inclusion of a 3-year lag period (HR 0.93, 95% CI 0.80-1.08).

DISCUSSION

PDE5I initiation in men with ED was associated with a lower risk of AD, particularly in those most frequently issued prescriptions. The differences between primary and sensitivity analyses highlight the need to explore the optimal lag period. To enhance the generalizability of our findings, a randomized controlled trial including both sexes and exploring various PDE5I doses would be beneficial to confirm the association between PDE5I and AD.

Incident dementia risk among patients with type 2 diabetes receiving metformin versus alternative oral glucose-lowering therapy: an observational cohort study using UK primary healthcare records

INTRODUCTION

4.2 million individuals in the UK have type 2 diabetes, a known risk factor for dementia and mild cognitive impairment (MCI). Diabetes treatment may modify this association, but existing evidence is conflicting. We therefore aimed to assess the association between metformin therapy and risk of incident all-cause dementia or MCI compared with other oral glucose-lowering therapies (GLTs).

RESEARCH DESIGN AND METHODS

We conducted an observational cohort study using the Clinical Practice Research Datalink among UK adults diagnosed with diabetes at ≥40 years between 1990 and 2019. We used an active comparator new user design to compare risks of dementia and MCI among individuals initially prescribed metformin versus an alternative oral GLT using Cox proportional hazards regression controlling for sociodemographic, lifestyle and clinical confounders. We assessed for interaction by age and sex. Sensitivity analyses included an as-treated analysis to mitigate potential exposure misclassification.

RESULTS

We included 211 396 individuals (median age 63 years; 42.8% female), of whom 179 333 (84.8%) initiated on metformin therapy. Over median follow-up of 5.4 years, metformin use was associated with a lower risk of dementia (adjusted HR (aHR) 0.86 (95% CI 0.79 to 0.94)) and MCI (aHR 0.92 (95% CI 0.86 to 0.99)). Metformin users aged under 80 years had a lower dementia risk (aHR 0.77 (95% CI 0.68 to 0.85)), which was not observed for those aged ≥80 years (aHR 0.95 (95% CI 0.87 to 1.05)). There was no interaction with sex. The as-treated analysis showed a reduced effect size compared with the main analysis (aHR 0.90 (95% CI 0.83 to 0.98)).

CONCLUSIONS

Metformin use was associated with lower risks of incident dementia and MCI compared with alternative GLT among UK adults with diabetes. While our findings are consistent with a neuroprotective effect of metformin against dementia, further research is needed to reduce risks of confounding by indication and assess causality.

South Asian, Black and White ethnicity and the effect of potentially modifiable risk factors for dementia: A study in English electronic health records

INTRODUCTION

We aimed to investigate ethnic differences in the associations of potentially modifiable risk factors with dementia.

METHODS

We used anonymised data from English electronic primary care records for adults aged 65 and older between 1997 and 2018. We used Cox regression to investigate main effects for each risk factor and interaction effects between each risk factor and ethnicity.

RESULTS

We included 865,674 people with 8,479,973 person years of follow up. Hypertension, dyslipidaemia, obesity and diabetes were more common in people from minority ethnic groups than White people. The impact of hypertension, obesity, diabetes, low HDL and sleep disorders on dementia risk was increased in South Asian people compared to White people. The impact of hypertension was greater in Black compared to White people.

DISCUSSION

Dementia prevention efforts should be targeted towards people from minority ethnic groups and tailored to risk factors of particular importance.

Trends in the incidence of dementia in people with hypertension in the UK 2000 to 2021

INTRODUCTION

We investigated trends in the incidence of dementia in UK adults with hypertension.

METHODS

Primary care electronic health records from IQVIA Medical Research Data UK, previously known as THIN, were used to identify 2,133,118 adults aged ≥40 years with hypertension over 2000 to 2021. The annual incidence rate and average annual percentage change in recorded dementia diagnoses were estimated and stratified by sex, 10-year age bands, Townsend deprivation quintiles and dementia subtype.

RESULTS

The crude incidence rate of dementia in people with hypertension increased from 1.98 (95% confidence internal [CI] 1.89-2.07) per 1000 person-years at risk (PYAR) in 2000 to 5.29 per 1000 PYAR (95% CI 5.07-5.53) in 2021, corresponding to an average annual increase of 4.1% (95% CI 3.3-5.0). Those aged ≥80 years, the most economically deprived (Townsend = 5), and Alzheimer's disease subtype reported the highest incidence rate within their respective categories.

DISCUSSION

The annual incidence rate of dementia in the hypertensive population has increased over the last 22 years.

Highlights

New dementia diagnosis in the hypertensive population has increased over 22 years.The Alzheimer's disease subtype reported the highest incidence rate in people with hypertension.Difference in dementia incidence between hypertensive females and males has reduced.Difference in dementia incidence among deprivation categories has reduced in recent years.

Causal evidence that herpes zoster vaccination prevents a proportion of dementia cases

The root causes of dementia are still largely unclear, and the medical community lacks highly effective preventive and therapeutic pharmaceutical agents for dementia despite large investments into their development. There is growing interest in the question if infectious agents play a role in the development of dementia, with herpesviruses attracting particular attention. To provide causal as opposed to merely correlational evidence on this question, we take advantage of the fact that in Wales eligibility for the herpes zoster vaccine (Zostavax) for shingles prevention was determined based on an individual's exact date of birth. Those born before September 2 1933 were ineligible and remained ineligible for life, while those born on or after September 2 1933 were eligible to receive the vaccine. By using country-wide data on all vaccinations received, primary and secondary care encounters, death certificates, and patients' date of birth in weeks, we first show that the percentage of adults who received the vaccine increased from 0.01% among patients who were merely one week too old to be eligible, to 47.2% among those who were just one week younger. Apart from this large difference in the probability of ever receiving the herpes zoster vaccine, there is no plausible reason why those born just one week prior to September 2 1933 should differ systematically from those born one week later. We demonstrate this empirically by showing that there were no systematic differences (e.g., in pre-existing conditions or uptake of other preventive interventions) between adults across the date-of-birth eligibility cutoff, and that there were no other interventions that used the exact same date-of-birth eligibility cutoff as was used for the herpes zoster vaccine program. This unique natural randomization, thus, allows for robust causal, rather than correlational, effect estimation. We first replicate the vaccine's known effect from clinical trials of reducing the occurrence of shingles. We then show that receiving the herpes zoster vaccine reduced the probability of a new dementia diagnosis over a follow-up period of seven years by 3.5 percentage points (95% CI: 0.6 - 7.1, p=0.019), corresponding to a 19.9% relative reduction in the occurrence of dementia. Besides preventing shingles and dementia, the herpes zoster vaccine had no effects on any other common causes of morbidity and mortality. In exploratory analyses, we find that the protective effects from the vaccine for dementia are far stronger among women than men. Randomized trials are needed to determine the optimal population groups and time interval for administration of the herpes zoster vaccine to prevent or delay dementia, as well as to quantify the magnitude of the causal effect when more precise measures of cognition are used. Our findings strongly suggest an important role of the varicella zoster virus in the etiology of dementia.

Association of blood pressure variability during acute care hospitalization and incident dementia

Background and objectives

Recognized as a potential risk factor for Alzheimer's disease and related dementias (ADRD), blood pressure variability (BPV) could be leveraged to facilitate identification of at-risk individuals at a population level. Granular BPV data are available during acute care hospitalization periods for potentially high-risk patients, but the incident ADRD risk association with BPV measured in this setting is unknown. Our objective was to evaluate the relation of BPV, measured during acute care hospitalization, and incidence of ADRD.

Methods

We retrospectively studied adults, without a prior ADRD diagnosis, who were admitted to a large quaternary care medical center in Southern California between January 1, 2013 and December 31, 2019. For all patients, determined BPV, calculated as variability independent of the mean (VIM), using blood pressure readings obtained as part of routine clinical care. We used multivariable Cox proportional hazards regression to examine the association between BP VIM during hospitalization and the development of incident dementia, determined by new ICD-9/10 coding or the new prescription of dementia medication, occurring at least 2 years after the index hospitalization.

Results

Of 81,892 adults hospitalized without a prior ADRD diagnosis, 2,442 (2.98%) went on to develop ADRD (2.6 to 5.2 years after hospitalization). In multivariable-adjusted Cox models, both systolic (HR 1.05, 95% CI 1.00-1.09) and diastolic (1.06, 1.02-1.10) VIM were associated with incident ADRD. In pre-specified stratified analyses, the VIM associations with incident ADRD were most pronounced in individuals over age 60 years and among those with renal disease or hypertension. Results were similar when repeated to include incident ADRD diagnoses made at least 1 or 3 years after index hospitalization.

Discussion

We found that measurements of BPV from acute care hospitalizations can be used to identify individuals at risk for developing a diagnosis of ADRD within approximately 5 years. Use of the readily accessible BPV measure may allow healthcare systems to risk stratify patients during periods of intense patient-provider interaction and, in turn, facilitate engagement in ADRD screening programs.

Inflammatory Diseases, Inflammatory Biomarkers, and Alzheimer Disease: An Observational Analysis and Mendelian Randomization

BACKGROUND AND OBJECTIVES

Whether chronic autoimmune inflammatory diseases causally affect the risk of Alzheimer disease (AD) is controversial. We characterized the relationship between inflammatory diseases and risk of AD and explored the role of circulating inflammatory biomarkers in the relationships between inflammatory diseases and AD.

METHODS

We performed observational analyses for chronic autoimmune inflammatory diseases and risk of AD using data from 2,047,513 participants identified in the UK Clinical Practice Research Datalink (CPRD). Using data of a total of more than 1,100,000 individuals from 15 large-scale genome-wide association study data sets, we performed 2-sample Mendelian randomizations (MRs) to investigate the relationships between chronic autoimmune inflammatory diseases, circulating inflammatory biomarker levels, and risk of AD.

RESULTS

Cox regression models using CPRD data showed that the overall incidence of AD was higher among patients with inflammatory bowel disease (hazard ratio [HR] 1.17; 95% CI 1.15-1.19; p = 2.1 × 10-4), other inflammatory polyarthropathies and systematic connective tissue disorders (HR 1.13; 95% CI 1.12-1.14; p = 8.6 × 10-5), psoriasis (HR 1.13; 95% CI 1.10-1.16; p = 2.6 × 10-4), rheumatoid arthritis (HR 1.08; 95% CI 1.06-1.11; p = 4.0 × 10-4), and multiple sclerosis (HR 1.06; 95% CI 1.04-1.07; p = 2.8 × 10-4) compared with the age (±5 years) and sex-matched comparison groups free from all inflammatory diseases under investigation. Bidirectional MR analysis identified relationships between chronic autoimmune inflammatory diseases and circulating inflammatory biomarkers. Particularly, circulating monokine induced by gamma interferon (MIG) level was suggestively associated with a higher risk of AD (odds ratio from inverse variance weighted [ORIVW] 1.23; 95% CI 1.06-1.42; p IVW = 0.007) and lower risk of Crohn disease (ORIVW 0.73; 95% CI -0.62 to 0.86; p IVW = 1.3 × 10-4). Colocalization supported a common causal single nucleotide polymorphism for MIG and Crohn disease (posterior probability = 0.74), but not AD (posterior probability = 0.03). Using a 2-sample MR approach, genetically predicted risks of inflammatory diseases were not associated with higher AD risk.

DISCUSSION

Our data suggest that the association between inflammatory diseases and risk of AD is unlikely to be causal and may be a result of confounding. In support, although inflammatory biomarkers showed evidence for causal associations with inflammatory diseases, evidence was weak that they affected both inflammatory disease and AD.

Association Between Retinal Nerve Fiber Layer Thickness and Incident Dementia in the European Prospective Investigation into Cancer in Norfolk Cohort

BACKGROUND

Retinal nerve fiber layer (RNFL) thickness may reflect cerebral status.

OBJECTIVE

This study assessed the relationship between RNFL thickness and incident all-cause dementia in the European Prospective Investigation into Cancer in Norfolk (EPIC-Norfolk) Eye Study.

METHODS

Glaucoma detection with variable corneal compensation (GDx-VCC) and Heidelberg Retinal Tomograph II (HRT II) derived global mean RNFL thickness from dementia-free participants at baseline within the EPIC-Norfolk Eye Study were analyzed. Incident dementia was identified through linkage to electronic medical records. Cox proportional hazard mixed-effects regression models adjusted for key confounders were used to examine the associations between RNFL thickness and incident dementia in four separate models.

RESULTS

6,239 participants were included with 322 cases of incident dementia and mean age of 67.5-years old, with 49.7% women (median follow-up 13.2-years, interquartile range (11.7 to 14.6 years). Greater RNFL thickness (GDx-VCC) was not significantly associated with a lower risk of incident dementia in the full adjusted model [HR per quartile increase 0.95; 95% CI 0.82-1.10]. Similarly, RNFL thickness assessed with HRT II was also not associated with incident dementia in any model (full adjusted model; HR per quartile increase: 1.06; [95% CI 0.93-1.19]. Gender did not modify any associations under study.

CONCLUSION

GDx-VCC and HRT II derived RNFL thickness are unlikely to be useful predictors of incident dementia. Higher resolution optical imaging technologies may clarify whether there are useful relationships between neuro-retinal morphology and brain measures.

Incidence, morbidity, mortality and disparities in dementia: A population linked electronic health records study of 4.3 million individuals

INTRODUCTION

We report dementia incidence, comorbidities, reasons for health-care visits, mortality, causes of death, and examined dementia patterns by relative deprivation in the UK.

METHOD

A longitudinal cohort analysis of linked electronic health records from 4.3 million people in the UK was conducted to investigate dementia incidence and mortality. Reasons for hospitalization and causes of death were compared in individuals with and without dementia.

RESULTS

From 1998 to 2016 we observed 145,319 (3.1%) individuals with incident dementia. Repeated hospitalizations among senior adults for infection, unknown morbidity, and multiple primary care visits for chronic pain were observed prior to dementia diagnosis. Multiple long-term conditions are present in half of the individuals at the time of diagnosis. Individuals living in high deprivation areas had higher dementia incidence and high fatality.

DISCUSSION

There is a considerable disparity of dementia that informs priorities of prevention and provision of patient care.

Trends in prevalence and incidence of registered dementia and trends in multimorbidity among patients with dementia in general practice in Flanders, Belgium, 2000-2021: a registry-based, retrospective, longitudinal cohort study

OBJECTIVES

With the ageing of our population, it seems plausible that the prevalence of both dementia and multimorbidity will increase in the following decades. The aim of this study is to examine the trends in prevalence and incidence of registered dementia and trends in multimorbidity in patients with dementia in general practice in Flanders.

DESIGN

Retrospective, longitudinal cohort study.

SETTING

Primary care practices across Flanders, Belgium.

PARTICIPANTS

Patients included in the Intego database.

METHODS

Data were collected from the Intego database, a Belgian general practice registration network, from 1 January 2000 to 31 December 2021. Joinpoint regression, the Cochran-Armitage test and Jonckheere-Terpstra test were used for the trend analysis.

RESULTS

Data from 149 492 unique patients aged 65 years and older were available. From 2000 to 2021, 3835 incident cases of dementia were found. The age-adjusted prevalence of registered dementia significantly increased during this study period, from 1.19% to 2.43% (average annual percentage change (AAPC) 3.3; 95% CI 2.7 to 4.0). Incidence increased from 3.68 to 5.86 per 1000 patient years overall (AAPC 1.8, 95% CI -2.0 to 5.7), but declined in recent years (annual percentage change -8.1, 95% CI -14.8 to -0.8). Almost three-quarters of the patients with dementia (74.8%) suffered from multimorbidity (three or more comorbidities) and this increased significantly during the study period (p=0.0031). By 2021, 86.7% and 74.8% of the patients with dementia suffered from two or more or three or more chronic conditions, respectively. Hypertension (47.9%), osteoarthritis (29.7%) and lipid metabolism disorders (25.7%) were the most prevalent conditions.

CONCLUSIONS

The prevalence of registered dementia doubled over a 22-year time period, mirroring the increasing health burden by this disease globally. Furthermore, three-quarters of the patients with dementia suffered from multimorbidity, underlining the urgent need to implement comorbidity management and patient-centred care in dementia.

Identification of dementia and MCI cases in health information systems: An Italian validation study

Introduction

The identification of dementia cases through routinely collected health data represents an easily accessible and inexpensive method to estimate the prevalence of dementia. In Italy, a project aimed at the validation of an algorithm was conducted.

Methods

The project included cases (patients with dementia or mild cognitive impairment [MCI]) recruited in centers for cognitive disorders and dementias and controls recruited in outpatient units of geriatrics and neurology. The algorithm based on pharmaceutical prescriptions, hospital discharge records, residential long‐term care records, and information on exemption from health‐care co‐payment, was applied to the validation population.

Results

The main analysis was conducted on 1110 cases and 1114 controls. The sensitivity, specificity, and positive and negative predictive values in discerning cases of dementia were 74.5%, 96.0%, 94.9%, and 79.1%, respectively, whereas in detecting cases of MCI these values were 29.7%, 97.5%, 92.2%, and 58.1%, respectively. The variables associated with misclassification of cases were also identified.

Discussion

This study provided a validated algorithm, based on administrative data, which can be used to identify cases with dementia and, with lower sensitivity, also early onset dementia but not cases with MCI.

Decreased renal function is associated with incident dementia: An IMRD-THIN retrospective cohort study in the UK

INTRODUCTION

Decreased renal function is a potential risk factor for dementia.

METHODS

This retrospective cohort study of 2.8 million adults aged ≥50 years used the IMRD-THIN database, representative of UK primary care, from January 1, 1995 to February 24, 2020. The associations between estimated glomerular filtration rate (eGFR) and urine albumin creatinine ratio (ACR) with incident all-cause dementia were analyzed using Cox regression.

RESULTS

In the eGFR cohort (n = 2,797,384), worsening renal dysfunction was associated with increased hazard of all-cause dementia, with greatest hazard at eGFR 15-30 ml/min/1.73min² (hazard ratio [HR] 1.26, 95% confidence interval [CI] 1.19-1.33). In the ACR cohort (n = 641,912), the hazard of dementia increased from ACR 3-30 mg/mmol (HR 1.13, 95% CI 1.10-1.15) to ACR > 30 mg/mmol (HR 1.25, 95% CI 1.18-1.33).

DISCUSSION

Worsening eGFR and albuminuria have graded associations with the risk of dementia, which may have significant implications for the care of patients with kidney disease.

Effectiveness of primary care psychological therapy services for the treatment of depression and anxiety in people living with dementia: Evidence from national healthcare records in England

Background

Depression and anxiety are common and deleterious in people living with dementia (PLWD). It is currently unknown whether routinely provided psychological therapy can help reduce these symptoms in PLWD. This study aimed to investigate improvements in depression and anxiety symptoms over the course of therapy offered in primary care psychological therapy services in PLWD and to compare outcomes to people without dementia.

Methods

National data from Improving Access to Psychological Therapies services (IAPT) across England linked with Hospital Episode Statistics data, the Mental Health Services Dataset, and HES-ONS mortality data were used to identify 1,549 PLWD who completed a course of psychological treatment in IAPT between 2012-2019 and a propensity score matched control group without identified dementia. Outcome measures included pre-post intervention changes in depression (PHQ-9) and anxiety (GAD-7) symptoms and therapy outcomes (reliable improvement, recovery, deterioration).

Findings

Symptoms of depression (t(1548)=31·05, p<·001) and anxiety (t(1548)=30·31, p<·001) improved in PLWD over the course of psychological therapy with large effect sizes (depression: d=-0·83; anxiety: d=-0·80). However, PLWD were less likely to reliably improve (OR=·75, 95%CI[·63,·88], p<·001) or recover (OR=·75, 95%CI[·64,·88], p=·001), and more likely to deteriorate (OR=1·35, 95%CI[1·03,1·78], p=·029) than a matched control sample without dementia.

Interpretation

Psychological therapy may be beneficial for PLWD with depression or anxiety, but it is currently not as effective as for people without dementia. More research is needed to improve access to psychological therapies and to understand this discrepancy and how therapies can be adapted to further improve outcomes.

Funding

This work was supported by the Alzheimer's Society.

No evidence that herpes zoster is associated with increased risk of dementia diagnosis

OBJECTIVE

To investigate whether herpes zoster (HZ) was associated with subsequent increased risk of dementia diagnosis.

METHODS

We conducted a historical cohort study using primary care electronic health records from the Clinical Practice Research Datalink in the United Kingdom. Individuals with incident HZ aged ≥40 years from 2000 to 2017 were matched with up to four individuals without HZ by age, sex, primary care practise and calendar time. The primary outcome was a new diagnosis of all-cause dementia. We used the Cox proportional hazards regression adjusting for demographic, lifestyle and clinical confounders to assess any association between HZ and dementia. We investigated interactions with sex, frailty index and antiviral treatment and conducted various sensitivity analyses.

RESULTS

The cohort comprised 177,144 individuals with HZ and 706,901 matched unexposed individuals (median age 65 years (IQR 55.1-75.0), 40% male) followed for a median duration of 4.6 years (IQR 2.0-8.1). In total, 26,585 (3%) patients had an incident dementia diagnosis recorded and 113,056 patients died (12.8%). HZ was associated with a small reduction in dementia diagnosis (adjusted HR 0.92 (95% CI 0.89-0.95)), occurring predominantly in frail individuals and females. For patients who were fit (578,115, 65%), no association was seen (adjusted HR 0.97, 95% CI 0.92-1.02). There was no association between HZ and a composite outcome of dementia or death (adjusted HR 1.00, 95% CI 0.99-1.02). Dementia risk did not vary by prescription of antiviral agents. Sensitivity analyses showed consistent results.

INTERPRETATION

HZ was not associated with increased dementia diagnosis in a UK primary care-based cohort.

Anticoagulant prescribing for atrial fibrillation and risk of incident dementia

OBJECTIVE

The aim of this study was to investigate the association between oral anticoagulant type (direct oral anticoagulants (DOACs) vs vitamin K antagonists (VKAs)) and incident dementia or mild cognitive impairment (MCI) among patients with newly diagnosed atrial fibrillation (AF).

METHODS

Using linked electronic health record (EHR) data from the Clinical Practice Research Datalink in the UK, we conducted a historical cohort study among first-time oral anticoagulant users with incident non-valvular AF diagnosed from 2012 to 2018. We compared the incidence of (1) clinically coded dementia and (2) MCI between patients prescribed VKAs and DOACs using Cox proportional hazards regression models, with age as the underlying timescale, accounting for calendar time and time on treatment, sociodemographic and lifestyle factors, clinical comorbidities and medications.

RESULTS

Of 39 200 first-time oral anticoagulant users (44.6% female, median age 76 years, IQR 68-83), 20 687 (53%) were prescribed a VKA and 18 513 (47%) a DOAC at baseline. Overall, 1258 patients (3.2%) had GP-recorded incident dementia, incidence rate 16.5 per 1000 person-years. DOAC treatment for AF was associated with a 16% reduction in dementia diagnosis compared with VKA treatment in the whole cohort (adjusted HR 0.84, 95% CI: 0.73 to 0.98) and with a 26% reduction in incident MCI (adjusted HR 0.74, 95% CI: 0.65 to 0.84). Findings were similar across various sensitivity analyses.

CONCLUSIONS

Incident EHR-recorded dementia and MCI were less common among patients prescribed DOACs for new AF compared with those prescribed VKAs.

What gets recorded, counts: dementia recording in primary care compared with a specialist database

BACKGROUND

databases of electronic health records are powerful tools for dementia research, but data can be influenced by incomplete recording. We examined whether people with dementia recorded in a specialist database (from a mental health and dementia care service) differ from those recorded in primary care.

METHODS

a retrospective cohort study of the population covered by Lambeth DataNet (primary care electronic records) between 2007 and 2019. Documentation of dementia diagnosis in primary care coded data and linked records in a specialist database (Clinical Records Interactive Search) were compared.

RESULTS

3,859 people had dementia documented in primary care codes and 4,266 in the specialist database, with 2,886/5,239 (55%) documented in both sources. Overall, 55% were labelled as having Alzheimer's dementia and 29% were prescribed dementia medication, but these proportions were significantly higher in those documented in both sources. The cohort identified from the specialist database were less likely to live in a care home (prevalence ratio 0.73, 95% confidence interval 0.63-0.85), have multimorbidity (0.87, 0.77-0.98) or consult frequently (0.91, 0.88-0.95) than those identified through primary care codes, although mortality did not differ (0.98, 0.91-1.06).

DISCUSSION

there is under-recording of dementia diagnoses in both primary care and specialist databases. This has implications for clinical care and for generalizability of research. Our results suggest that using a mental health database may under-represent those patients who have more frailty, reflecting differential referral to mental health services, and demonstrating how the patient pathways are an important consideration when undertaking database studies.

Comparative differences in musculoskeletal pain consultation and analgesic prescription for people with dementia: a UK-wide matched cohort study

ABSTRACT

Painful musculoskeletal conditions are common in older adults; however, pain identification, assessment, and management are reported to be suboptimal for people with dementia. Adequate pain management is an integral aspect of care for people with dementia to prevent or delay negative outcomes, such as behavioural and psychological changes, emergency department attendance, and premature nursing home admission. This study aims to examine musculoskeletal consultations and analgesic prescriptions for people with dementia compared with those for people without dementia. A dementia cohort (n = 36,582) and matched cohort were identified in the Clinical Practice Research Datalink (a UK-wide primary care database). Period prevalence for musculoskeletal consultations and analgesic prescriptions was described, and logistic regression applied to estimate associations between dementia and musculoskeletal consultation or analgesic prescription from the time of dementia diagnosis to 5 years after diagnosis. People with dementia had a consistently (over time) lower prevalence and odds of musculoskeletal consultation and analgesic prescription compared with people without dementia. The evidence suggests that pain management may be suboptimal for people with dementia. These results highlight the need to increase awareness of pain and use better methods of pain assessment, evaluation of treatment response, and acceptable and effective management for people with dementia, in primary care.

Exposure to Air Pollution in Relation to Risk of Dementia and Related Outcomes: An Updated Systematic Review of the Epidemiological Literature

BACKGROUND

Dementia is a devastating neurologic condition that is common in older adults. We previously reviewed the epidemiological evidence examining the hypothesis that long-term exposure to air pollution affects dementia risk. Since then, the evidence base has expanded rapidly.

OBJECTIVES

With this update, we collectively review new and previously identified epidemiological studies on air pollution and late-life cognitive health, highlighting new developments and critically discussing the merits of the evidence.

METHODS

Using a registered protocol (PROSPERO 2020 CRD42020152943), we updated our literature review to capture studies published through 31 December 2020, extracted data, and conducted a bias assessment.

RESULTS

We identified 66 papers (49 new) for inclusion in this review. Cognitive level remained the most commonly considered outcome, and particulate matter (PM) remained the most commonly considered air pollutant. Since our prior review, exposure estimation methods in this research have improved, and more papers have looked at cognitive change, neuroimaging, and incident cognitive impairment/dementia, though methodological concerns remain common. Many studies continue to rely on administrative records to ascertain dementia, have high potential for selection bias, and adjust for putative mediating factors in primary models. A subset of 35 studies met strict quality criteria. Although high-quality studies of fine particulate matter with aerodynamic diameter ≤ 2.5 μ m (PM 2.5 ) and cognitive decline generally supported an adverse association, other findings related to PM 2.5 and findings related to particulate matter with aerodynamic diameter ≤ 10 μ m (PM 10 , NO 2 , and NO x ) were inconclusive, and too few papers reported findings with ozone to comment on the likely direction of association. Notably, only a few findings on dementia were included for consideration on the basis of quality criteria.

DISCUSSION

Strong conclusions remain elusive, although the weight of the evidence suggests an adverse association between PM 2.5 and cognitive decline. However, we note a continued need to confront methodological challenges in this line of research. https://doi.org/10.1289/EHP8716.

The rising tide of dementia deaths: triangulation of data from three routine data sources using the Clinical Practice Research Datalink

BACKGROUND

Dementia is currently the leading certified underlying cause of death in England. We assess how dementia recording on Office for National Statistics death certificates (ONS) corresponded to recording in general practice records (GP) and Hospital Episode Statistics (HES).

METHODS

Retrospective study of deaths (2001-15) in 153 English General Practices contributing to the Clinical Practice Research Datalink, with linked ONS and HES records.

RESULTS

Of 207,068 total deaths from any cause, 19,627 mentioned dementia on the death certificate with 10,253 as underlying cause; steady increases occurred from 2001 to 2015 (any mention 5.3 to 15.4 %, underlying cause 2.7 to 10 %). Including all data sources, recording of any dementia increased from 13.2 to 28.6 %. In 2015, only 53.8 % of people dying with dementia had dementia recorded on their death certificates. Among deaths mentioning dementia on the death certificate, the recording of a prior diagnosis of dementia in GP and HES rose markedly over the same period. In 2001, only 76.3 % had a prior diagnosis in GP and/or HES records; by 2015 this had risen to 95.7 %. However, over the same period the percentage of all deaths with dementia recorded in GP or HES but not mentioned on the death certificate rose from 7.9 to 13.3 %.

CONCLUSIONS

Dementia recording in all data sources increased between 2001 and 2015. By 2015 the vast majority of deaths mentioning dementia had supporting evidence in primary and/or secondary care. However, death certificates were still providing an inadequate picture of the number of people dying with dementia.

Infectious Disease Burden and the Risk of Alzheimer's Disease: A Population-Based Study

BACKGROUND

Previous studies suggested a link between various infectious pathogens and the development of Alzheimer's disease (AD), posing the question whether infectious disease could present a novel modifiable risk factor.

OBJECTIVE

To assess whether infectious disease burden due to clinically apparent infections is associated with an increased risk of AD.

METHODS

We conducted a population-based nested case-control study using the United Kingdom Clinical Practice Research Datalink. We included all dementia-free subjects ≥50 years of age enrolling in the database between January 1988 and December 2017. Each case of AD identified during follow-up was matched with up to 40 controls. Conditional logistic regression estimated adjusted odds ratios (ORs) with 95% confidence intervals (CIs) of AD associated with ≥1 infection diagnosed > 2 years before the index date compared with no infection during the study period. We further stratified by time since first infection and cumulative number of infections.

RESULTS

The cohort included overall 4,262,092 individuals (mean age at cohort entry 60.4 years; 52% female). During a median follow-up of 10.5 years, 40,455 cases of AD were matched to 1,610,502 controls. Compared with having no burden of infectious disease, having a burden of infectious disease was associated with an increase in the risk of AD (OR, 1.05; 95% CI, 1.02 to 1.08). The risk increased with longer time since first infection, peaking after 12-30 years (OR, 1.11; 95% CI, 1.05-1.17). The risk did not increase with cumulative number of infections.

CONCLUSION

The overall risk of AD associated with infectious disease burden was small but increased gradually with longer time since first infection.

The identification and validity of congenital malformation diagnoses in UK electronic health records: A systematic review

PURPOSE

To describe the methods used to identify and validate congenital malformation diagnoses recorded in UK electronic health records, and the results of validation studies.

METHODS

Medline and Embase were searched for publications between 1987 and 2019 that involved identifying congenital malformations from UK electronic health records using diagnostic codes. The methods and code-lists used to identify congenital malformations, and the methods and results of validations, were examined.

RESULTS

We retrieved 54 eligible studies; 36 identified congenital malformations from primary care data and 18 from secondary care data alone or in combination with birth and/or death records. Identification in secondary care data relied on codes from the 'Q' chapter for congenital malformations in ICD-10. In contrast, studies using primary care data frequently used additional codes outside of the 'P' chapter for congenital malformation diagnoses in Read, although the exact codes used were not always clear. Eight studies validated diagnoses identified in primary care data. The positive predictive value was highest (80%-100%) for congenital malformations overall, major malformations, and heart defects although the validity of the reference standard used was often uncertain. It was lowest for neural tube defects (71%) and developmental hip dysplasia (56%).

CONCLUSIONS

Studies identifying congenital malformations from primary care data provided limited details about the methods used. The few validation studies were limited to diagnoses recorded in primary care. Further assessments of all measures of validity in both data sources and of other malformation subgroups are needed, using robust reference standards and adhering to reporting guidelines.

Indicators of dementia disease progression in primary care: An electronic health record cohort study

BACKGROUND AND PURPOSE

The objectives were to assess the feasibility and validity of using markers of dementia-related health as indicators of dementia progression in primary care, by assessing the frequency with which they are recorded and by testing the hypothesis that they are associated with recognised outcomes of dementia. The markers, in 13 domains, were derived previously through literature review, expert consensus, and analysis of regional primary care records.

METHODS

The study population consisted of patients with a recorded dementia diagnosis in the Clinical Practice Research Datalink, a UK primary care database linked to secondary care records. Incidence of recorded domains in the 36 months after diagnosis was determined. Associations of recording of domains with future hospital admission, palliative care, and mortality were derived.

RESULTS

There were 30,463 people with diagnosed dementia. Incidence of domains ranged from 469/1000 person-years (Increased Multimorbidity) to 11/1000 (Home Pressures). An increasing number of domains in which a new marker was recorded in the first year after diagnosis was associated with hospital admission (hazard ratio for ≥4 domains vs. no domains = 1.24; 95% confidence interval = 1.15-1.33), palliative care (1.87; 1.62-2.15), and mortality (1.57; 1.47-1.67). Individual domains were associated with outcomes with varying strengths of association.

CONCLUSIONS

Feasibility and validity of potential indicators of progression of dementia derived from primary care records are supported by their frequency of recording and associations with recognised outcomes. Further research should assess whether these markers can help identify patients with poorer prognosis to improve outcomes through stratified care and targeted support.

Associations of BMI and Serum Urate with Developing Dementia: A Prospective Cohort Study

CONTEXT

Recent studies have suggested that a higher body mass index (BMI) and serum urate levels were associated with a lower risk of developing dementia. However, these reverse relationships remain controversial, and whether serum urate and BMI confound each other is not well established.

OBJECTIVES

To investigate the independent associations of BMI and urate, as well as their interaction with the risk of developing dementia.

DESIGN AND SETTINGS

We analyzed a cohort of 502 528 individuals derived from the UK Biobank that included people aged 37-73 years for whom BMI and urate were recorded between 2006 and 2010. Dementia was ascertained at follow-up using electronic health records.

RESULTS

During a median of 8.1 years of follow-up, a total of 2138 participants developed dementia. People who were underweight had an increased risk of dementia (hazard ratio [HR] = 1.91, 95% confidence interval [CI]: 1.24-2.97) compared with people of a healthy weight. However, the risk of dementia continued to fall as weight increased, as those who were overweight and obese were 19% (HR = 0.81, 95%: 0.73-0.90) and 22% (HR = 0.78, 95% CI: 0.68-0.88) were less likely to develop dementia than people of a healthy weight. People in the highest quintile of urate were also associated with a 25% (HR = 0.75, 95% CI: 0.64-0.87) reduction in the risk of developing dementia compared with those who were in the lowest quintile. There was a significant multiplicative interaction between BMI and urate in relation to dementia (P for interaction = 0.004), and obesity strengthens the protective effect of serum urate on the risk of dementia.

CONCLUSION

Both BMI and urate are independent predictors of dementia, and there are inverse monotonic and dose-response associations of BMI and urate with dementia.

Implications of the Use of Algorithmic Diagnoses or Medicare Claims to Ascertain Dementia

INTRODUCTION

Formal dementia ascertainment with research criteria is resource-intensive, prompting the growing use of alternative approaches. Our objective was to illustrate the potential bias and implications for study conclusions introduced through the use of alternate dementia ascertainment approaches.

METHODS

We compared dementia prevalence and risk factor associations obtained using criterion-standard dementia diagnoses to those obtained using algorithmic or Medicare-based dementia ascertainment in participants of the baseline visit of the Aging, Demographics, and Memory Study (ADAMS), a Health and Retirement Study (HRS) sub-study.

RESULTS

Estimates of dementia prevalence derived using algorithmic or Medicare-based ascertainment differ substantially from those obtained using criterion-standard ascertainment. Use of algorithmic or Medicare-based dementia ascertainment can, but does not always, lead to risk factor associations that substantially differ from those obtained using criterion-standard ascertainment.

DISCUSSION/CONCLUSIONS

Absolute estimates of dementia prevalence should rely on samples with formal dementia ascertainment. The use of multiple algorithms is recommended for risk factor studies when formal dementia ascertainment is not available.

Validity of Acute Cardiovascular Outcome Diagnoses Recorded in European Electronic Health Records: A Systematic Review

BACKGROUND

Electronic health records are widely used in cardiovascular disease research. We appraised the validity of stroke, acute coronary syndrome and heart failure diagnoses in studies conducted using European electronic health records.

METHODS

Using a prespecified strategy, we systematically searched seven databases from dates of inception to April 2019. Two reviewers independently completed study selection, followed by partial parallel data extraction and risk of bias assessment. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value estimates were narratively synthesized and heterogeneity between sensitivity and PPV estimates were assessed using I2.

RESULTS

We identified 81 studies, of which 20 validated heart failure diagnoses, 31 validated acute coronary syndrome diagnoses with 29 specifically recording estimates for myocardial infarction, and 41 validated stroke diagnoses. Few studies reported specificity or negative predictive value estimates. Sensitivity was ≤66% in all but one heart failure study, ≥80% for 91% of myocardial infarction studies, and ≥70% for 73% of stroke studies. PPV was ≥80% in 74% of heart failure, 88% of myocardial infarction, and 70% of stroke studies. PPV by stroke subtype was variable, at ≥80% for 80% of ischaemic stroke but only 44% of haemorrhagic stroke. There was considerable heterogeneity (I2 >75%) between sensitivity and PPV estimates for all diagnoses.

CONCLUSION

Overall, European electronic health record stroke, acute coronary syndrome and heart failure diagnoses are accurate for use in research, although validity estimates for heart failure and individual stroke subtypes were lower. Where possible, researchers should validate data before use or carefully interpret the results of previous validation studies for their own study purposes.

Using clinical registries, administrative data and electronic medical records to improve medication safety and effectiveness in dementia

PURPOSE OF REVIEW

Clinical registries, routinely collected administrative data and electronic medical records (EMRs) provide new opportunities to investigate medication safety and effectiveness. This review outlines the strengths and limitations of these data, and highlights recent research related to safe and effective medication use in dementia.

RECENT FINDINGS

Clinical registries, administrative data and EMRs facilitate observational research among people often excluded from randomized controlled trials (RCTs). Larger sample sizes and longer follow-up times permit research into less common adverse events not apparent in RCTs. The validity of diagnoses recorded in administrative data and EMRs remains variable, although positive predictive values are typically high and sensitivity is low. Dispensing records are a rich source of data for estimating medication exposure. Recent research has investigated medications and prescribing patterns as risk factors for incident dementia, strategies to alleviate behavioural symptoms and the management of comorbidity. Common study protocols and common data models are examples of distributed network approaches increasingly used to conduct large and generalizable multi-database studies across different countries.

SUMMARY

Greater availability of electronic health data provides important opportunities to address evidence-practice gaps in relation to medication use and safety in people with dementia.

How well can electronic health records from primary care identify Alzheimer's disease cases?

Background

Electronic health records (EHR) from primary care are emerging in Alzheimer’s disease (AD) research, but their accuracy is a concern. We aimed to validate AD diagnoses from primary care using additional information provided by general practitioners (GPs), and a register of dementias.

Patients and methods

This retrospective observational study obtained data from the System for the Development of Research in Primary Care (SIDIAP). Three algorithms combined International Statistical Classification of Diseases (ICD-10) and Anatomical Therapeutic Chemical codes to identify AD cases in SIDIAP. GPs evaluated dementia diagnoses by means of an online survey. We linked data from the Register of Dementias of Girona and from SIDIAP. We estimated the positive predictive value (PPV) and sensitivity and provided results stratified by age, sex and severity.

Results

Using survey data from the GPs, PPV of AD diagnosis was 89.8% (95% CI: 84.7–94.9). Using the dataset linkage, PPV was 74.8 (95% CI: 73.1–76.4) for algorithm A1 (AD diagnoses), and 72.3 (95% CI: 70.7–73.9) for algorithm A3 (diagnosed or treated patients without previous conditions); sensitivity was 71.4 (95% CI: 69.6–73.0) and 83.3 (95% CI: 81.8–84.6) for algorithms A1 (AD diagnoses) and A3, respectively. Stratified results did not differ by age, but PPV and sensitivity estimates decreased amongst men and severe patients, respectively.

Conclusions

PPV estimates differed depending on the gold standard. The development of algorithms integrating diagnoses and treatment of dementia improved the AD case ascertainment. PPV and sensitivity estimates were high and indicated that AD codes recorded in a large primary care database were sufficiently accurate for research purposes.

The validity of dementia diagnoses in routinely collected electronic health records in the United Kingdom: A systematic review

PURPOSE

The purpose of the study is to assess the validity of codes or algorithms used to identify dementia in UK electronic health record (EHR) primary care and hospitalisation databases.

METHODS

Relevant studies were identified by searching the MEDLINE/EMBASE databases from inception to June 2018, hand-searching reference lists, and consulting experts. The search strategy included synonyms for "Dementia", "Europe", and "EHR". Studies were included if they validated dementia diagnoses in UK primary care or hospitalisation databases, irrespective of validation method used. The Quality Assessment for Diagnostic Accuracy Studies-2 (QUADAS-2) tool was used to assess risk of bias.

RESULTS

From 1469 unique records, 14 relevant studies were included. Thirteen validated individual diagnoses against a reference standard, reporting high estimates of validity. Most reported only the positive predictive value (PPV), with estimates ranging between 0.09 and 1.0 and 0.62 and 0.85 in primary care and hospitalisation databases, respectively. One study performed a rate comparison, indicating good generalisability of dementia diagnoses in The Health Improvement Network (THIN) database to the UK population. Studies were of low methodological quality. As studies were not comparable, no summary validity estimates were produced.

CONCLUSION

While heterogenous across studies, reported validity estimates were generally high. However, the credibility of these estimates is limited by the methodological quality of studies, primarily resulting from insufficient blinding of researchers interpreting the reference test. Inadequate reporting, particularly of the specific codes validated, hindered comparison of estimates across studies. Future validation studies should make use of more robust reference tests, follow established reporting guidelines, and calculate all measures of validity.