Longitudinal analyses of obesity determinants and associated health outcomes in the U.S. middle-aged and older adults

This dissertation consists of two sub-studies. Sub-study 1 attempted to examine the longitudinal effects of individual demographics, state-level socioeconomic status (SES), density of fast food restaurants, and proportion of people who walk to work on body mass index (BMI) among adults aged 50 years and older from 2000 to 2010. Data were drawn from the 2000--2010 Health and Retirement Study (HRS) and the 2010 U.S. Census. Respondents who lived at the same census tract during 2000--2010 (N=6,156) were included. A three-level growth model was fit to model BMI trajectories. BMI significantly increased over time showing both a linear and quadratic decelerating trajectory (p<.001). Women living in states with a lower state-level SES had higher BMI level while men living in states with higher state-level SES had a higher BMI (b=-0.242, p=.013). For people living in states with a higher proportion of people who walk to work, Hispanics had higher BMI level at the baseline and lower BMI growth rate, compared with non-Hispanic whites (b=-0.033, p<.001). Evidence suggests that we should provide sex responsive interventions and better walking environments to tackle obesity epidemic. Sub-study 2 investigated the effects of Part D implementation on health outcomes among the U.S. older adults. Data from the 2004-2008 HRS respondents who further participated in the HRS 2005-2007 Prescription Drug Study and consented to share their Medicare claims were analyzed (N=746). A panel ordered logistic regression with a difference-in-differences approach was used to examine the Part D effect on patients' health outcomes before and after Part D implementation. People with continuous Part D enrollment from 2006-2008 were less likely to have a worse self-rated health than those who were not enrolled in Part D (OR=0.48; p<.05). A higher Charlson Comorbidity Index score was associated with a higher likelihood of having worse self-rated overall health, worse mental health, and worse activity daily living impairment (ORs=1.12, 1.17, and 1.36, respectively; all ps<.001). The Part D implementation appeared to have a positive effect on older adults' overall health status. Reducing healthcare cost would likely encourage older adults to utilize more needed medications and help maintain better health.