White-Black disparities in disability in the older population are consistently reported in the literature, and are usually ascribed to differences in socio-economic, health, and cognitive status. However, the role of modifiable influences on disability, such as health and lifestyle behaviors or health care utilization on these differences is less clear. This dissertation examines: (1) longitudinal White-Black differences in disability and the potential contributions of distinct health behaviors to these differences; (2) White-Black differences in the effects of health care utilization on trajectories of disability; and (3) whether cognition mediates the effects of health behaviors on disability in Whites and in Blacks, independent of established confounders for these relationships.

This dissertation uses longitudinal data from the Asset and Health Dynamics among the Oldest Old study (AHEAD). Trajectories of disability in basic (ADL) and instrumental (IADL) activities of daily living are fit using mixed effects models with time-varying predictors. The mediation effect is tested using a multilevel mediation model.

Results indicate that health behaviors close the residual White-Black gap in IADL trajectories but not the residual gap in ADL trajectories. Physical activity participation and maintenance of a normal weight or overweight status resulted in lower ADL and IADL disability levels over time among Whites. None of the health behaviors influenced longitudinal trajectories of disability in Blacks. Short-stay nursing home and home health care utilization was associated with lower ADL and IADL disability levels over time among Blacks. Cognition mediated the effect of physical activity participation on ADL and cognitive IADL in Whites but not in Blacks. That is, physical activity participation had positive effects on ADL and IADL disability both directly, and indirectly through beneficial effects on cognition.

Modifiable influences on disability, such as health and lifestyle behaviors and health care utilization should be targeted by intervention programs and regulatory policies in order to narrow or eliminate the White-Black disability disparities. Such interventions may represent effective avenues for achieving the goals of Healthy People 2010.