Sleep as a Modifiable Determinant of Gender, Racial, and Intersectional Disparities in Cognitive Aging

Abstract

Sleep problems, such as insomnia and sleep apnea, have been associated with increased risk for cognitive impairment and dementia in later life; however, considerable heterogeneity in the presentation of sleep problems has made it difficult to pinpoint the specific mechanisms underlying sleep—cognition associations. Moreover, convergent health disparities have been reported for sleep and cognitive health outcomes in later life, yet it is unknown whether sociodemographic disparities in sleep operate as mediators of sociodemographic disparities in cognitive aging. A deeper understanding of these associations is necessary to inform the development of tailored interventions aimed at reducing inequalities in cognitive aging.

This dissertation examined the associations between sleep and cognition among older adults and identified potential sociodemographic group differences in three separate studies. Study 1 examined the associations between distinct insomnia symptoms and subsequent cognitive performance across multiple domains in a longitudinal epidemiological sample, and additionally investigated whether insomnia—cognition associations are mediated through mental and physical health pathways and moderated by gender. Study 2 examined whether different patterns in the chronicity of difficulty initiating sleep are associated with subsequent cognitive functioning and decline in a nationally representative sample of older adults, and whether patterns of difficulty initiating sleep and associations between difficulty initiating sleep and cognition differ across four race-gender intersectional groups. Study 3 examined whether diagnosed sleep apnea and sleep apnea risk mediate racial disparities in cognition in a cross-sectional regional sample of Black and White older adults, and whether associations among race, sleep apnea, and cognition are conditional upon socioeconomic status.

Together, all three studies provide evidence for insomnia and sleep apnea as contributors to sociodemographic disparities in cognitive aging and suggest that these disparities may arise from both greater exposure to as well as differential impact of poor sleep health across gender, racial, and intersectional identities. The use of more comprehensive measures of sleep health across studies reveal that difficulty initiating sleep may be the insomnia phenotype most consequential for subsequent cognitive function, particularly when experienced intermittently, and that assessing sleep apnea diagnosis status does not accurately reflect disease presence in the community. Results also highlight the importance of intersectionality in health disparities, particularly with respect to the synergistic effects of racism and classism for health care access and health outcomes. Overall, findings from each of these studies offer several potential targets for interventions aimed at reducing inequalities in cognitive aging.