The Dynamics of Disability and Functional Change in an Elderly Cohort: Results from the Alameda County Study

OBJECTIVE: To examine changes in functional status over time by age, gender, and ethnicity in a representative sample of older persons. DESIGN: Six-year prospective cohort study. SETTING: Alameda County, California. PARTICIPANTS: 508 persons 65 years old and older at baseline in 1984. MAIN OUTCOME MEASURES: Activities of daily living (ADL) dependence, mobility impairment, and functioning on an 18-item scale. RESULTS: The prevalence of ADL dependence and mobility impairment at baseline increased with age, while function decreased. Particularly striking differences occurred for those 80 and older. Changes in function over the 6-year follow-up showed a similar pattern. While death rates for males were higher, females had poorer initial functioning, and surviving females declined more than surviving males. The incidence of ADL dependence and mobility impairment during follow-up was similar for males and females, although females survived longer with incident disability than did males. Blacks had poorer baseline functioning, more ADL dependence and mobility impairment, and declined more than non-Blacks during follow-up. Some of the baseline difference in function between Blacks and non-Blacks was due to higher rates of chronic illness and co-morbidity. In spite of the general downward trend in functioning over the 6 years, 13% of the males and 20% of the females improved. CONCLUSION: Age-related changes in function for older persons are complex and result in much heterogeneity. Clarifying the reasons for such heterogeneity is an important and challenging area of research.