Effect of ethnicity on sleep: complexities for epidemiologic research.

Study Objectives: The goal of this study was to examine whether there were ethnic differences in polysomnographically recorded sleep, either in the controlled laboratory environment or in the home setting.
Design: Prospective study of ethnic differences in stress physiology and sleep.
Setting: Two sleep recordings were performed on consecutive nights in a hospital-based sleep laboratory, followed 1 to 4 weeks later by a third sleep recording in the subject's home.
Participants: 51 employed healthy adult subjects, aged 15 to 50 years. 24 self-identified as black, and 27 as white.
Interventions: None.
Measurements and Results: Blacks had less slow wave sleep than did whites in both the sleep laboratory and in the home. Blacks had significantly more slow wave sleep at home compared to the hospital setting, while the reverse was true for whites. This location-by-ethnicity interaction could not be accounted for by depression ratings or social class.
Conclusions: The home setting is generally considered to be more ecologically valid than the controlled hospital-based laboratory setting for the monitoring of sleep. These data suggest that ethnicities may respond differentially to the sleeping environment. This observation may need to be taken into account in future epidemiologic studies of sleep.