Compared to whites, African Americans are more likely to suffer from a constellation of health problems referred to as “cardiovascular and metabolic diseases:” high blood pressure, diabetes, and stroke. Things like diet, exercise, and smoking contribute to those conditions, but when researchers control for those behaviors, the disparity persists. Now scientists are examining an unexpected factor that could be driving these disparities in heart disease: sleep.
Think of sleep as a time when the body tidies up its hormonal systems. People who consistently don’t get enough sleep have increases in ghrelin, a hunger hormone, and decreases in leptin, a hormone that helps people feel sated. That might lead to increased eating during the day. Even if it doesn’t, sleep deprivation wreaks havoc on other key hormones and proteins, like insulin and the inflammatory markers C-reactive protein and interleukin-6—which are, in turn, linked to cardiovascular and metabolic diseases.
David Curtis, a human development researcher at Auburn University, decided to try to determine whether differences in sleep could explain some of these racial disparities in cardiometabolic diseases. He and researchers from Northwestern University and the University of Wisconsin recruited 426 white and African American men and women and equipped them with Fitbit-type devices that can monitor sleep. They took some biological measurements, such as blood pressure, waist circumference, and insulin resistance, and then measured how long they slept each night for seven nights. It wasn’t enough just to be in bed: The wrist-bands they wore also measured how often the participants woke up in the night.