Waking at 3 a.m. may echo an older pattern. Historian A. Roger Ekirch analyzed over 500 references in diaries, court records, medical texts and literature and found that Western societies once practiced segmented sleep: a first sleep after dusk, a waking period around midnight called the watch, and a second sleep. People prayed, reflected on dreams, wrote by candlelight, visited neighbors or committed petty crimes. In a 1992 study, Thomas Wehr kept seven healthy men in darkness 14 hours a day for a month; after catching up on sleep they settled into two four-hour blocks with two to three hours awake between, marked by elevated prolactin. The episode also covers the siesta and how electric light and air conditioning eroded both rhythms.
Then come the extremes: online biohackers on the Everyman and Uberman schedules, and Buckminster Fuller's 1940s Dymaxion schedule of a 30-minute nap every six hours. The hosts explain why short naps miss slow wave deep sleep and the glymphatic clearing of amyloid beta, and cite the National Sleep Foundation's position that there is no evidence such schedules are effective. In real emergencies, though, sailors, astronauts and military pilots have used structured napping, and researchers have measured its limits.
Time magazine reported in 1943 that Fuller kept the Dymaxion schedule for two years, quitting because associates insisted on sleeping like other men.
Claudio Stampi studied solo sailors and ran a 49-day lab experiment with a young man sleeping three hours a day.
NASA research led by David Dinges found longer naps beat shorter ones and helped working memory, while sleep inertia could cause grogginess for up to an hour.
A U.S. Air Force fatigue countermeasure report said naps during continuous operations should last at least 45 minutes, with two hours ideal.
Italian Air Force pilots on a two-hours-on, four-hours-off cycle cut total sleep but kept vigilance with virtually no microsleeps.
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