Healthy behaviors and onset of functional disability in older adults: results of a national longitudinal study

Objectives: To examine the combined effect of healthy behaviors on the development of functional disability in an elderly cohort.

Design: Prospective cohort study.

Setting: Taiwan Longitudinal Study in Aging from 1989, 1993, 1996, 1999, and 2003.

Participants: A national sample of 1,940 men and 1,247 women aged 60 and older without functional disability at baseline.

Measurements: Functional disability was defined as difficulty with activities of daily living: taking a bath or walking 200 to 300 m. Time to functional disability was the age at midpoint between the first occurrence of disability onset in the survey year and prior survey year. Considering that the onset of disability is probably a precursor of death, for those who died without disability, time to disability onset was set at the midpoint between the last follow-up and death year. Four healthy behaviors were measured: not smoking, moderate alcohol consumption, regular exercise, and sleeping 6 to 8 hours per day. A Cox proportional hazards model with time-dependent covariates was used to analyze the association between age at the first functional disability and prior healthy behavior, after controlling for sex, time-varying disease status, marital status, and education.

Results: Healthy behaviors were linked to the onset of functional disability. Participants who performed one or more healthy behaviors were 15% to 75% less likely to be disabled than those who performed none.

Conclusion: In the population studied, healthy behaviors were associated with lower incidence of functional disability. As the number of healthy behaviors increased, the likelihood of disability decreased.