Objectives: To identify predictors of institutionalization in a community-based cohort of older adults.
Design: Prospective, longitudinal. After initial assessment at study entry, surviving participants were reassessed in a series of approximately biennial waves until October 2001; baseline for the current analysis was Wave 2 (1989-91).
Setting: Largely rural, blue-collar community in the mid-Monongahela Valley of southwestern Pennsylvania.
Participants: A population-based cohort of 1,147 adults, aged 66 and older (mean 74.1) at baseline, who were not already institutionalized and who had complete data on all variables of interest.
Measurements: Cox proportional hazards models were used to identify predictors of institutionalization from among selected variables measured at baseline, including age, sex, education, marital status, living arrangements, ability to perform instrumental activities of daily living (IADLs), depressive symptoms, number of prescription medications (as an index of overall morbidity), self-reported social support, hospitalization during the preceding year, and cognitive functioning. Dementia was defined according to the operational criteria of the Diagnostic and Statistical Manual of Mental Disorders, Third Edition, Revised, and by a Clinical Dementia Rating of 0.5 or greater, based on a standardized clinical assessment. The outcome variable was institutionalization, defined as entry into in a nursing home.
Results: Significant predictors of institutionalization were dementia (hazard ratio (HR)=5.09, 95% confidence interval (CI)=2.92-8.84), measured as a time-dependent variable; older age (HR=1.06, 95% CI=1.03-1.10); IADL disability (HR=1.31, 95% CI=1.15-1.50); worse/less social support (HR=1.27, 95% CI=1.10-1.46); and number of prescription medications (HR=1.21, 95% CI=1.11-1.32), measured at baseline. The interaction between number of prescription drugs and dementia was also significant, suggesting that prescription medication count had less effect on institutionalization in those with dementia than in those without.
Conclusion: Dementia emerged as the most potent risk factor for institutionalization in this 12-year community-based epidemiological study. Medical burden conferred greater vulnerability to institutionalization in nondemented persons than in those with dementia.