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abstract: Background and purpose: Regular physical activity (PA) provides benefits for cognitive health and helps to improve or maintain quality of life among older adults. Objective PA measures have been increasingly used to overcome limitations of self-report measures. The purpose of this study was to investigate the association of objectively measured PA and sedentary time with cognitive function among older adults. Methods: Participants were recruited from the parent REasons for Geographic and Racial Differences in Stroke (REGARDS) Study. ActicalTM accelerometers provided estimates of PA variables, including moderate-to-vigorous PA (MVPA), high light PA (HLPA), low light PA (LLPA) and sedentary time, for 4-7 consecutive days. Prevalence and incidence of cognitive impairment were defined by the Six-Item Screener. Letter fluency, animal fluency, word list learning and Montreal Cognitive Assessment (orientation and recall) were conducted to assess executive function and memory. Results: Of the 7,339 participants who provided accelerometer wear data > 4 days (70.1 ± 8.6 yr, 54.2% women, 31.7% African American), 320 participants exhibited impaired cognition. In cross-sectional analysis, participants in the highest MVPA% quartile had 39% lower odds of cognitive impairment than those in the lowest quartile (OR: 0.61, 95% C.I.: 0.39-0.95) after full adjustment. Further analysis shows most quartiles of MVPA% and HLPA% were significantly associated with executive function and memory (P<0.01). During 2.7 ± 0.5 years of follow-up, 3,385 participants were included in the longitudinal analysis, with 157 incident cases of cognitive impairment. After adjustments, participants in the highest MVPA% quartile had 51% lower hazards of cognitive impairment (HR: 0.49, 95% C.I.: 0.28-0.86). Additionally, MVPA% was inversely associated with change in memory z-scores (P<0.01), while the highest quartile of HLPA% was inversely associated with change in executive function and memory z-scores (P<0.01). Conclusion: Higher levels of objectively measured MVPA% were independently associated with lower prevalence and incidence of cognitive impairment, and better memory and executive function in older adults. Higher levels of HLPA% were also independently associated with better memory and executive function. The amount of MVPA associated with lower risk of cognitive impairment (259 min/week) is >70% higher than the minimal amount of MVPA recommended by PA guidelines. / Dissertation/Thesis / Doctoral Dissertation Physical Activity, Nutrition and Wellness 2015

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The ways in which white Americans understand the racial landscape and their own racial identities are not well understood. Through the lens of the racial past, in this study I investigate how memory operates within the white racial frame, the dominant white-centric worldview, to uphold systemic racism and to maintain whites’ collective and individual identities. Through a narrative analysis of original in-depth interviews conducted with 44 ordinary white southerners – lifetime residents of Greensboro, North Carolina – who lived through the legal segregation and civil rights eras, this research demonstrates the interviewees’ contemporary investment in positive notions of the white self and white society. The respondents' autobiographical narratives of life during legal segregation, a time of overt white supremacy, are typified by nostalgia for a childhood era of safety, security, and "good" race relations. Interviewees' narratives of the civil rights era, including nonviolent student sit-in protests for which Greensboro is known and school desegregation, have themes of disruption, danger, and white victimization. Overall, respondents portray Jim Crow segregation as a calm and peaceful time and the civil rights era as chaotic and harmful to whites, at the same time as they acknowledge, to a limited extent, the unfairness of Jim Crow's blatant racial inequalities. In this work I propose the concepts white victimology, white protectionism, and white moral identity. I argue that white victimology – whites' perception, largely imagined, of their own racial victimization – is a major ideological and emotional facet of the white racial frame, whereby whites dismiss the historical and contemporary reality of white racism. My analysis demonstrates that white victimology is a primary way in which whites assert themselves, individually and collectively, as racial innocents and "good" people. In this work I also conceptualize the dynamic of white protectionism, explanatory and rhetorical ways in which whites "rescue" white acquaintances and family members from potential accusations of racism. Ultimately, I argue that whites' investment in perpetuating white dominance and upholding the white racial frame occurs through white moral identity-making, myriad active and subtle ways that whites continue to construct themselves positively and construct people of color, especially black Americans, negatively.