Life-Course Disparities in Dementia Risk: Disentangling the Contributions of Socioeconomic Status and Vascular Risk Factors

Abstract

Disproportionately high risk of dementia among racial and ethnic minorities in the U.S. has been attributed to life-course exposures to adverse conditions such as lower educational attainment, and prevention strategies have often focused on optimizing lifestyle risk factors such as diet and physical activity in order to modify key vascular risk factors. However, there are gaps in our understanding of when and how these disparities arise. Most studies have not considered additional disparities in early-life education quality, and whether achieving optimal levels of these risk factors may be less effective in populations with social vulnerability due to structural barriers to attaining or maintaining health. Furthermore, early-life divergence of dementia risk among those with different education levels may render midlife lifestyle modifications insufficient in reducing dementia risk. In this dissertation, we aimed to describe the components of racial disparities in dementia risk related to the educational experience and assess the extent to which educational disparities in dementia risk operate through mid-life vascular risk factors and lifestyle. In Chapter 1, we conducted a literature review to assess whether and how measures of educational attainment and quality are utilized in the development of norms for standard cognitive screening measures. We identified estimates of relationships between race, education quality and dementia, and calculated the adjusted association between race and dementia had education quality been equalized between Black and White participants. In Chapter 2, we assessed the relationship between education and dementia among all participants and among those with incident stroke in a cohort of 13,368 Black and White older adults in four U.S. communities, then tested whether there is substantial mediation of the relationship between educational attainment and dementia by mid-life vascular risk factors. Finally, we used the same methods and data source in Chapter 3 to assess whether midlife diet quality and physical activity are associated with dementia risk differentially by educational attainment and whether they mediate the relationship between education and dementia. We found that present studies are limited in their consideration of education quality and that if education quality were equalized across groups by race, without changing disparities in attainment, racial disparities in dementia would be reduced by about half. We further demonstrated that better diet quality in midlife is associated with lower dementia risk only among those with very high educational attainment, and that while a substantial proportion of the relationship between education and dementia risk was mediated through mid-life vascular risk factors, modification of risk factors is unlikely to fully address the large educational disparities in dementia risk. Future work should seek to consistently incorporate education quality in order to better understand the sources of disparities and to identify the etiologic windows over the life-course when lifestyle modifications may be effective. Prevention efforts must also address disparities in socioeconomic resources leading to divergent early-life educational experiences and other structural determinants of mid-life vascular risk factors.