Skeletal Muscle Adiposity, Cognitive Function and Sleep Patterns in Adults of African Ancestry: Insights from the CARDIA and Tobago Health Studies

Skeletal muscle adipose tissue infiltration (myosteatosis) increases cardiometabolic diseases risk. Myosteatosis is greater in individuals of African ancestry (AA) and in women, who are at higher risk of Alzheimer's disease and Related Dementia (ADRD). Visceral adiposity has been linked to dementia and cognitive decline, yet the relationship between myosteatosis and cognition is unclear. Given the importance of myosteatosis in cardiometabolic health, it is critical to examine the association of myosteatosis with cognitive function and its decline and determine if associations are independent of cardiometabolic disorders. Additionally, the impact of emerging lifestyle risk factors, like short sleep duration, on myosteatosis, has not been thoroughly explored, especially in AA Caribbean populations. This doctoral dissertation fills these gaps by investigating associations between myosteatosis, cognitive function, and sleep duration in AA and White adults. The first aim was to examine the association between calf myosteatosis and cognitive function in middle and older-aged AA Caribbean women. Myosteatosis was inversely associated with information processing speed measured by the Digit-Symbol-Substitution-Test (DSST), an early indicator of cognitive decline. The second aim was to extend these findings by exploring the relationship between abdominal myosteatosis and 5-year cognitive decline in middle-aged U.S. White and AA men and women. Over five years, greater myosteatosis predicted cognitive decline, as measured by DSST, in White and female participants. The third aim was to examine the association of sleep duration with adiposity (general, central, and muscle) and cognitive function in AA Caribbeans. Longer sleep duration was significantly associated with lower BMI, reduced waist circumference, and lower calf myosteatosis. Despite these beneficial associations of longer sleep duration with adiposity, we found no association between sleep duration and cognitive function. In summary, these findings emphasize the novel role of myosteatosis in brain health. We also show for the first time that sleep duration is an important risk factor for myosteatosis among AA individuals. Our work has significant public health implications, particularly for vulnerable and understudied populations such as AA middle-aged individuals, and women. Targeted interventions to mitigate dementia risk factors and improve overall health in diverse populations are critically needed.