Identifying dementia using medical data linkage in a longitudinal cohort study: Lothian Birth Cohort 1936.

BACKGROUND: The Lothian Birth Cohort 1936 (LBC1936) is a longitudinal study of ageing with well-characterised assessments, but until now, it has relied on self-report or proxies for dementia such as cognitive tests. Our aims were twofold: a) to describe a framework for identifying dementia in a cohort study. b) to report the age-specific incidence and prevalence of all-cause dementia and dementia subtypes in 865 individuals in the LBC1936. METHODS: Electronic Health Records (EHR) of all participants were reviewed, and relevant information was extracted to form case vignettes for everyone with any record of cognitive dysfunction. The EHR data sources include hospital and clinic letters, general practitioner and hospital referrals, prescribed medications, imaging and laboratory results. Death certificate data were obtained separately. Clinician assessments were performed when there was concern about a participant's cognition. A diagnosis of probable dementia, possible dementia, or no dementia was agreed upon by a consensus diagnostic review board, comprised of a multidisciplinary team of clinical dementia experts who reviewed case vignettes and clinician assessment letters. For those with probable dementia, a subtype was also determined, where possible. We compared the agreement between our newly ascertained dementia diagnoses with the existing self-reported dementia diagnoses. RESULTS: Self-reported dementia diagnoses were positive in only 17.8% of ascertained dementia diagnoses. The EHR review identified 163/865 (18.8%) individuals as having cognitive dysfunction. At the consensus diagnostic review board, 118/163 were diagnosed with probable all-cause dementia, a prevalence of 13.6%. Age-specific dementia prevalence increased with age from 0.8% (65-74.9 years) to 9.93% (85-89.9 years). Prevalence rates for women were higher in nearly all age groups. The most common subtype was dementia due to Alzheimer disease (49.2%), followed by mixed Alzheimer and cerebrovascular disease (17.0%), dementia of unknown or unspecified cause (16.1%), and dementia due to vascular disease (8.5%). CONCLUSIONS: We present a robust systematic framework and guide for other cohort teams wanting to ascertain dementia diagnoses. The newly ascertained dementia diagnosis provides vital data for further analyses of LBC1936 to allow exploration of lifecourse predictors of dementia.

The incidence, baseline predictors, and outcomes of dementia in an incident cohort of Parkinson's disease and controls.

BACKGROUND: There are few long-term data on the incidence, baseline predictors, and outcomes of dementia in Parkinson's disease (PD) from prospective community-based incident cohorts. METHODS: The PINE study prospectively identified all incident PD patients in Aberdeen along with age-sex-matched, community-based controls who consented to standardized annual life-long follow-up. Each year, a clinical expert reviewed the diagnosis of PD and the presence of dementia according to DSM-IV-based criteria. Age-sex stratified incidence rates for dementia in PD and controls were calculated and compared with hazard ratios (HR) adjusted for age, sex, education, and socioeconomic status. Cox proportional-hazard modelling was used to assess baseline predictors for PD dementia and the influence of dementia on survival and institutionalization. RESULTS: 201 patients (mean age 72.6yrs) and 260 controls (mean age 75.4yrs) were followed for median 9.5 years. The incidence of dementia was 7.4 (PD) versus 2.1 (controls) per 100 person-years (adjusted HR 6.0, 95%CI 4.1-8.7), with a sixfold increase from under 60 to over 80 years in PD but no sex difference. Independent baseline predictors of PD dementia were older age at diagnosis, self-reported cognitive symptoms, dream enactment, lower MMSE scores, worse motor UPDRS scores, and the ApoE genotype. PD dementia increased the rates of subsequent death and institutionalization (32.0 and 26.9 per 100 person-years, respectively). CONCLUSION: The incidence of dementia in PD is high, increases markedly with age, is increased in those with baseline subjective cognitive symptoms as well as other established risk factors, and is associated with high rates of death and institutionalization.