Endocrine and cognitive effects of a radically polyphasic sleep schedule

To increase time spend awake and thereby productive, voluntary sleep restriction is a common phenomenon in industrialized societies, however with detrimental effects on cognitive functioning and health. In this study, we studied 8 young healthy male university students (21 – 28 y) who decided to change their sleep habits to a radically polyphasic schedule of one 20 minute nap every 4 hours without any extended core sleep phase, resulting in a cumulative sleep amount of only 2h/day. Before entering this schedule, subjects underwent a physiological and psychiatric health screening, plus a 24h physiological monitoring including polysomnography and blood sampling every 30 minutes. In addition, subjects were assessed with tests of declarative and procedural memory, fluid reasoning, and psychomotor vigilance. After five weeks of polyphasic sleep, the 24h monitoring was repeated. All but one of the test subjects terminated the polyphasic sleep schedule during the first three weeks, mainly due to a too strong impact on their social lives. The remaining subject did not show any cognitive impairments in any of the assessed tasks after 5 weeks of radically polyphasic sleep. While the pattern of cortisol and melatonin release did not differ between the two test sessions, growth hormone release was strongly suppressed overall and in addition strongly changed the pattern of secretion: Instead of one major peak during the first hours of sleep, six smaller peaks were observed after each nap.