How does Mobility Change over Time for Older Adults, and How are Changes Influenced by Cognitive Functioning?

Mobility, which includes life space and driving behaviors, is an important functional domain for older adults (e.g., Webber, Porter, & Menec, in press). Low mobility is associated with sensory, physical, and cognitive deficits (e.g., Anstey, Wood, Lord, & Walker, 2005). However, few studies have investigated how mobility changes over time. This dissertation contains three longitudinal articles that explored mobility changes, with an emphasis on driving and cognition, among community-dwelling older adults. The first paper investigated patterns of driving self-regulation (i.e., adjustment of driving behaviors) among control-group participants from the Advanced Cognitive Training for Independent and Vital Elderly (ACTIVE) study (N=548). Self-regulation was defined by driving space, frequency, and perceived difficulty. Growth mixture models revealed one subgroup of drivers ( Decreasers ) that showed declines in their driving, and two subgroups that were stable over time. Relative to the stable groups, Decreasers showed significantly more depressive symptoms and lower reasoning, speed of processing (Useful Field of View Test [UFOV]), self-rated health, balance, and everyday functioning at baseline. The second paper examined mobility changes in ACTIVE participants with psychometrically defined mild cognitive impairment (MCI; N=304). Group differences in life space and driving (space, frequency, and difficulty) were evaluated using random effects models, which were adjusted for baseline demographics, health, depression, balance, attrition, and cognitive training participation. Relative to normal participants, participants with MCI showed reduced baseline mobility for all outcomes, as well as faster rates of decline for driving frequency and difficulty. Finally, the third paper examined three-year changes in mobility for control-group participants in the Staying Keen in Later Life (SKILL) study (N=370). Outcomes were life space and driving (space, frequency, and difficulty). Latent change models revealed significant correlations between: changes in life space and age; changes in driving frequency and complex reaction time (Road Sign Test); and changes in driving difficulty and age, gender, mental status, and complex reaction time (Road Sign Test). Taken together, the articles in this dissertation show that older adults exhibit distinct patterns of mobility over time, and that demographic, health, and cognitive factors are associated with these patterns