Objective: To determine the contribution of Alzheimer’s disease to the mortality experience of the community.
Design: A 12-year prospective epidemiological study of an older rural community-based cohort in the United States.
Materials and Methods. The Monongahela Valley Independent Elders Survey (MoVIES) followed a cohort aged 65+ years through biennial examinations. Repeated assessments of all participants included the Mini Mental State Examination (MMSE), ability to perform instrumental activities of daily living (IADLs) using the OARS scale, depressive symptoms using the modified Center for Epidemiological Studies- Depression scale (mCES-D), and overall morbidity as reflected by number of prescription drugs. Cognitively impaired participants and a subgroup of matched controls underwent repeated clinical assessments to diagnose dementia including Alzheimer’s disease (AD) according to DSM-III-R and NINCDS-ADRDA criteria. 1227 cohort members with complete data on all variables of interest were followed for up to 12 years, with 542 deaths occurring during this period. Predictors of mortality were determined using Cox proportional hazards analytic models.
Results: There were 273 incident cases of AD. On its own, AD significantly predicted mortality with a hazard ratio (HR) of 2.8, which dropped to 1.5 after adjusting for other significant covariates. These were male sex (HR 1.6), age (HR 1.08 for every year increase), numbers of functional impairments (HR 1.4 for 1-3 impaired activities and HR 2.1 for 4 or more impairments), depression (HR 1.3), and prescription drugs (HR 1.17 per drug. The Population Attributable Risk (PAR) due to AD was 3.2% after adjusting for these covariates. When men and women were examined separately, AD significantly increased the risk of mortality only among women.
Conclusion: Among individuals in a representative community-based cohort, the presence of AD increased the risk of death by 50%, after adjusting for other mortality predictors; 3.2% of the risk of mortality in the cohort was attributable to AD. Quantification of the contribution of AD to mortality can be useful in discussing prognosis with families and also aid in the assessment of overall public health burden.
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