Sydney Allison Jones: Physical Activity and Sedentary Behavior During the Retirement Transition (Under the direction of Kelly R. Evenson) The health of older adults is of increasing public health importance given current demographic trends. Physical activity can improve quality of life and delay impairment in later life. However, many older adults are not physically active and engage in large quantities of sedentary behavior (sitting or reclining while awake), which is linked to increased risk of disease. The retirement transition may be an opportune window to promote physical activity in later life. Retirement involves shifts in routines, social networks, and access to resources and has been linked to physical activity and sedentary behavior changes. However, existing research on physical activity and sedentary behavior during the retirement transition lacks socioeconomic diversity and excludes non-leisure domains of physical activity. Moreover, social and environmental factors that influence physical activity after retirement remain unexplored. This research sequentially combined quantitative and qualitative studies to characterize physical activity and sedentary behavior during the retirement transition. First, we described longitudinal patterns in physical activity and television watching by retirement status and socioeconomic position in a diverse cohort of 4,091 United States adults. Retirement was associated with increased recreational walking, household activity, and television watching but decreased overall moderate-to-vigorous physical activity, particularly among persons of lower socioeconomic position. Second, we identified correlates of within-person changes in walking after retirement among 928 retirees from the same cohort. Correlates included health and iv perceptions of the neighborhood environment, and differed for recreational and transport walking. Third, we interviewed 15 retired women to identify facilitators and barriers to physical activity after retirement. Physical activity after retirement was influenced by: leisure-time physical activity habits over the lifespan, prior occupational physical activity, concurrent life transitions, health, social interaction and support, and the community environment. Together this research provided substantive knowledge regarding patterns of physical activity and television watching associated with retirement, and the first exploration to date of correlates of walking during the retirement transition. These three interrelated studies can benefit community leaders, public health practitioners, and researchers by guiding the development and targeting of interventions among retirees, including prioritizing community-level changes that support physical activity and reduce sedentary behavior among retirees. v ACKNOWLEDGEMENTS I would like to thank Kelly Evenson and the other members of my dissertation committee for their expertise and encouragement. As my advisor, Kelly has provided more than five years of guidance and mentorship. I am particularly grateful t...