Are there ethnic differences in sleep architecture?

The possibility of ethnic differences in sleep architecture was initially examined in conjunction with studies of sleep apnea (study 1). This possibility was then examined in another cohort of patients to determine whether the results might generalize (study 2). Polysomnography was obtained in both cohorts as part of larger protocols investigating sympathetic nervous system activity, blood pressure, and sleep. Sleep monitoring took place in an inpatient clinical research center of a university hospital. Study I focused on sleep apnea physiology and involved volunteers with sleep apnea who were otherwise healthy. Study 2 focused on differences in stress reactivity between American Black and White subjects and involved hypertensive and normotensive volunteers who were otherwise healthy. Analyses include 61 participants from study 1 and 35 participants from study 2. Ethnicity in both cohorts was determined by self-report. Participants in both studies were monitored during sleep with traditional polysomnography including electroencephalography (EEG), electromyography (EMG), electrooculography (EOG), and oximetry. In Study 1, Blacks had longer TST (P < 0.01), more REM sleep (P < 0.05), and less WASO (P < 0.05) than Whites. After controling for RDI, Blacks had longer TST and spent a smaller percentage of time in deep sleep (P < 0.05). In study 2, Blacks had longer TST and REM sleep, lower percent deep sleep, and lower percent deep sleep controling for RDI (P < 0.05). In two separate studies, Blacks had longer TST, more minutes of REM, and lower percentage deep sleep. These findings suggest possible ethnic differences in sleep architecture. (C) 2002 Wiley-Liss, Inc.