With individuals living longer and the aging of the Baby Boomer cohort, the US is experiencing a demographic revolution. Given that risk of dementia increases substantially with age, this aging revolution will drastically increase the prevalence of dementia unless interventions to prevent or delay it are found. Physical activity has been identified as a potential intervention to lower the risk of dementia and/or improve/maintain cognitive function. Therefore, we propose to undertake a pilot study using data from 2 Waves (1992 and 2004) of the National Long-term Care Survey (NLTCS) to examine potential associations between physical activity and cognitive health (i.e. risk of dementia and cognitive function). The NLTCS, longitudinal in structure, is a large, nationally-representative sample of individuals from both the community and institutions. Our specific aims include: (1) to examine the relationship between physical activity and risk of Alzheimer's disease (AD) and other dementias; (2) to examine the relationship between physical activity and change in cognitive function from baseline to follow up; (3) to explore the relationship between dose of physical activity and risk of dementia, as well as change in cognitive function; and (4) to explore the effectiveness of various types of physical activity on cognitive health. We will use logistic regression analysis, controlling for potential confounding factors such as age, education, race, cardiovascular factors and socialization, with physical activity as our independent variable of interest. Dependent variables will include incident AD, dementia and cognitive impairment, as well as change in cognitive function.