Prolonged sleep under Stone Age conditions.

STUDY OBJECTIVES:We report on a unique experiment designed to investigate the impact of prehistoric living conditions on sleep-wake behavior. METHODS:A group of five healthy adults were assessed during life in a Stone Age-like settlement over two months. RESULTS:The most notable finding was that nocturnal time in bed and estimated sleep time, as measured by actigraphy, markedly increased during the experimental period compared to the periods prior to and following the experiment. These increases were primarily driven by a phase-advance shift of sleep onset. Subjective assessments of health and functioning did not reveal any relevant changes across the study. CONCLUSIONS:Our observations provide further evidence for the long-held belief that the absence of modern living conditions is associated with an earlier sleep phase and prolonged sleep duration. COMMENTARY:A commentary on this article appears in this issue on page 723.