PROJECT SUMMARY Stroke is the third leading cause of disability globally, and the number of incident strokes is expected to increase substantially as the size of the population aged 65 and older grows. After a stroke, some patients experience an accelerated decline in cognitive and functional ability, while disability stabilizes for other patients. However, little is known about why cognitive trajectories vary widely after stroke. One theory of cognitive aging is that a more complex living environment is potentially protective against cognitive decline by allowing for opportunities for exercise, recreation, and social activities. One way to measure individuals’ living environments is through studying their life-space, which is the size and pattern of the physical area in which they spend their time. Studies have found that life-space is associated with better cognitive function in older adults. However, there is a lack of research in identifying the mechanisms by which life-space is protective against cognitive decline post-stroke. We will leverage two studies to evaluate the relationship between life- space and long-term cognitive decline after stroke. Here, we propose a study that aims to (1) estimate the effects of components of life-space on cognitive decline in the years following stroke in a large observational cohort from the Cardiovascular Health Study (n=5,888), (2) characterize the life-space of stroke survivors using geolocation data in the StrokeCog cohort (n=270) and (3) prospectively evaluate the effect of components of life-space on cognitive change after stroke. Our findings will advance our understanding of factors that affect the long-term cognitive trajectory after ischemic stroke. This award will also support the career development of Sylvie Dobrota Lai, a doctoral student in the Department of Epidemiology and Population Health at the Stanford School of Medicine. Through completing the proposed research, the applicant will pursue training in (1) the epidemiology of aging, (2) clinical issues in stroke patients, (3) geospatial data collection and analysis, and (4) career development. The applicant will be supported by a mentorship team comprising of experts in aging epidemiology, statistics, and neurology. Through this fellowship, the applicant will develop strong methodological skills, gain subject expertise, and become a more independent epidemiologic researcher. The proposed study will provide a strong foundation for the applicant’s future academic research career and position her to become a leader in aging research.