Racial disparities in sleep-related cardiac function in young, healthy adults: Implications for cardiovascular-related health.

STUDY OBJECTIVES Considerable evidence shows that individuals from marginalized racial/ethnic groups in the US experience greater rates of sleep disturbance and cardiovascular complications. Because sleep is a modifiable factor that is critically involved in cardiovascular health, improved understanding of the association between sleep and cardiovascular health during early adulthood can prevent cardiovascular disparities. This study examined racial/ethnic differences in cardiovascular function during sleep using heart-rate and heart-rate-variability analyses. METHODS Participants in this laboratory-based sleep study included healthy, "good sleepers" who were in early adulthood and resided in the US at the time of participation [14 non-Hispanic Black (NHB; age=30.9(6.6), 57% female), 12 Asian (Asian, age=26.0(5.2), 42% female), and 24 non-Hispanic white (NHW; age=24.6(5.8), 79% female)]. RESULTS After adjusting for demographic factors and an apnea-hypopnea index, we found significantly higher heart rate within NREM Stage 2 (N2) (b=-22.6, p=.04) and REM sleep (b=-25.8, p=.048) and lower heart rate variability during N2 sleep (b=-22.6, p=.04) among NHB individuals compared to NHW individuals. Further, NHB and Asian participants demonstrated significantly lower percent of time in slow wave sleep (SWS) compared to NHW participants (NHB: b=-22.6, p=.04; Asian: b=-22.6, p=.04). Individuals' percent of time in SWS significantly mediated differences in heart rate during N2 [indirect=0.94, 95% CI (0.03, 2.68)] and REM sleep [indirect=1.02, 95% CI (0.04, 3.04)]. CONCLUSIONS Our results showed disparities in sleep-related cardiovascular function in early adulthood that are mediated by SWS. These data suggest targeting sleep health in early adulthood might help reduce cardiovascular disease burden on individuals from marginalized groups.