Fig. 1.

Study protocol. Open bars represent room light (<40 lx). Black bars represent scheduled polysomnography-recorded sleep. Time of day is plotted as relative clock hour with scheduled waketime arbitrarily assigned a value of 0800 hours and all other times referenced to this value. Shaded areas indicate scheduled wakefulness in dim light (<1 lx). B, breakfast; D, dinner; L, lunch; S, snack. Subjects were allowed three brief scheduled breaks per day to stand up and retrieve meals and use the toilet for bowel movements <3 m from the bed. Outside of scheduled breaks, subjects were given a urinal or bedpan when needed. Wakefulness and subject compliance during the constant posture protocol were verified via continuous monitoring by research staff and electroencephalography (EEG) recordings.