Are sleep and depression independent or overlapping risk factors for cardiometabolic disease?

Sleep duration, sleep continuity, and depression are associated with cardiovascular disease and metabolic disorders. Despite the well-established relationship between sleep and depression, few studies examine these characteristics simultaneously in the development of cardiometabolic disease. Here, we review available studies that include measures of both sleep and depression in relation to cardiometabolic outcomes (cardiovascular disease, diabetes, and the metabolic syndrome). In general, data show that independent of depression, sleep continuity is a risk factor for cardiovascular disease, and short or long sleep duration is a risk factor for diabetes and the metabolic syndrome. Results for associations between sleep duration and cardiovascular disease, and associations between sleep continuity and metabolic disease, are more mixed. Regarding depression, there is preliminary evidence that depression increases risk for cardiovascular disease, independent of sleep continuity. However, there are insufficient data to address whether relationships between depression and cardiovascular and metabolic disease are independent of sleep duration. A number of biobehavioral mechanisms, including inflammation, hypothalamic and sympathetic dysregulation, and obesity and health behaviors, may account for the relationships among sleep, depression, and cardiometabolic disease. After summarizing these mechanisms, we discuss limitations of the extant literature and suggest directions for future research.