Weber A L, Cary M S, Connor N, Keyes P
Sleep. 1980;2(3):347-54.
A sighted college student maintained a sleep-wake cycle longer than 24 hr in his everyday environment for more than half of nearly four years. The range of sleep-wake periods and the amount and regularity of sleep are consistent with those found in time-free environments. Episodes of 24 hr periodicity suggest that social cues or obligations are effective entraining agents. He reported more sleep difficulties while on a 24 hr than a non-24-hr schedule.
