title: When the human circadian system is caught napping: evidence for endogenous rhythms close to 24 hours.
abstract: It is now well acknowledged that napping constitutes an inherent component of the human circadian system. To date, however, few studies have examined the effects of spontaneous napping on human free-running rhythms. This study investigated the free-running circadian periods of rest/activity and body core temperature in a group of young subjects who were permitted to nap during their time in isolation. Based on the frequency of self-reported sleep bouts, subjects were classified as Nappers or Nonnappers. Nappers exhibited free-running rhythms in both rest/activity and body core temperature that were not significantly different from 24 hours. Nappers showed a tendency for shorter free-running periods in both variables, when compared with Nonnappers. These findings emphasize the need for careful reassessment of data obtained from traditional free-run protocols.
authors.affiliation: Department of Psychiatry, Cornell University Medical College, White Plains, New York 10605.
authors.forename: S S
authors.initials: SS
authors.lastname: Campbell
authors.forename: D
authors.initials: D
authors.lastname: Dawson
authors.forename: J
authors.initials: J
authors.lastname: Zulley
mesh_terms: D000328:Adult; D002940:Circadian Rhythm / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D012890:Sleep / Q000502:physiology*