| Accumulating epidemiological evidence suggests a relationship between short sleep duration and cardiovascular disease. The biological mechanisms underlying this relationship, however, are not yet fully understood. The three studies contained in this dissertation will contribute to our overall understanding of this relationship.In the first study, the effects of partial restriction on plasma leptin were examined. Contrary to previous research, it was observed that five nights of partial sleep restriction significantly increased plasma leptin levels. Increases were significantly greater among women, a population that has been inadequately represented in prior studies. Additionally, it was observed that recovery sleep, compared to further sleep restriction, decreased plasma leptin levels.The second study focused on the effects of sleep restriction on adiponectin. This study is the first to document changes in adiponectin levels in response to sleep restriction. Notably, a strong sex by ethnicity interaction was observed, in which female participants were observed to have significant changes in adiponectin: levels in Caucasian women decreased significantly while levels in African American women increased significantly. These changes could not be explained through differences in body mass index.The third study examined the effects of sleep restriction on levels of C-reactive protein (CRP), IL-6, and cortisol. Sleep restriction did not significantly change CRP levels in the total sample however, levels of IL-6 and cortisol increased and differential vulnerability were observed for both IL-6 and cortisol. Further, a subset of the healthy participants was found to be in the 'high risk for future cardiovascular events' category, based on baseline CRP levels this population responded differently to the effects of sleep restriction compared to those participants with 'normal' baseline CRP levels.Results from these studies provide preliminary evidence for a differential vulnerability to the effects of sleep restriction on biological markers of cardiovascular risk. In particular, women appear to have a more reactive adipocyte-derived response to sleep restriction, although the directionality of effects with respect to subsequent effects on health may be related to race/ethnicity in some domains. These findings suggest a more complex relationship between sleep duration and cardiovascular risk than has been previously proposed. |
