Background: Many older persons who are highly vulnerable do not develop functional dependence, whereas some older persons with low vulnerability do develop functional dependence. We conducted this study to determine the combined effects of baseline vulnerability and precipitating events on the development of functional dependence.
Methods: We analyzed data from two prospective, population-based cohort studies. The development cohort included 799 community-living persons, 72 years of age and older, who were independent in their activities of daily living (ADLs). The validation cohort included 1,051 comparable persons. Participants were classified by baseline vulnerability, defined on the basis of physical performance, cognitive status, and age, and by exposure to potential precipitating events, determined from information gathered from acute care hospital admissions. The primary outcome was the onset of functional dependence, defined as a new disability in one or more of the seven ADLs at the 1-year follow-up interview or admission to a skilled nursing facility prior to the 1-year interview.
Results: Functional dependence developed in 109 (13.6%) participants in the development cohort and in 100 (9.3%) participants in the validation cohort. The rates of functional dependence for the low, intermediate, and high vulnerability groups were 7.1%, 17.2%, and 40.1% (p<.001) in the development cohort and 4.8%, 15.0%, and 28.0% (p<.001) in the validation cohort. For the four categories (none, mild, moderate, severe) of precipitating events, the rates of functional dependence were 9.0%, 19.4%, 27.3%, and 53.2% (p<.001 ) in the development cohort and 5.1%, 12.0%, 28.2%, and 53.3% (p<.001) in the validation cohort. For both cohorts, when baseline vulnerability and precipitating events were analyzed in cross-stratified format, the rate of functional dependence increased progressively from low-risk to high-risk groups in all directions (double-gradient phenomenon). The contributions of baseline vulnerability and precipitating events to the development of functional dependence were independent and statistically significant.
Conclusions: Among community-living older persons, baseline vulnerability and precipitating hospital events contribute independently to the development of functional dependence and should each be targeted for intervention when developing strategies aimed at forestalling the onset of functional dependence.