Explaining the effect of gender on functional transitions in older persons.

BACKGROUND Women live longer but experience greater disability than men. The reasons for this gender difference in disability are not well understood. OBJECTIVE Our objectives were to determine if the higher prevalence of disability in women is due to greater incidence of disability, longer duration of disability, or both, and to identify factors that potentially explain these gender differences. METHODS 754 community-living persons aged 70 and older who were non-disabled (required no personal assistance) in four essential activities of daily living (ADLs) were assessed monthly for disability for up to 6 years. A multi-state extension of the proportional hazards model was used to determine the effects of gender on transitions between states of no disability, mild disability, severe disability, and death, and to evaluate potential mediators of these effects. RESULTS Women were more likely to make the transition from no disability to mild disability and less likely to make the transitions from mild to no disability and from both mild and severe disability to death. The gender difference in the transitions between no disability and mild disability was largely explained by differences in gait speed and physical activity, but gender difference in transitions to death persisted despite adjustment for multiple potential mediators. CONCLUSION The higher prevalence of disability in women versus men is due to a combination of higher incidence and longer duration, resulting from lower rates of recovery and mortality among disabled women.