A 2-WEEK SLEEP EXTENSION IN SLEEPY NORMALS

Thirty-four healthy, normal young men and women (21-35 years), with no sleep complaints and a normal screening polysomnogram, some with shor t (less than or equal to 6-minute) and some with long (greater than or equal to 16-minute) average daily sleep latencies on a screening mult iple sleep latency test, were studied on two baseline nights (8 hours) and in the ''sleepy'' group, for 14 consecutive nights of extended (1 0-hour) or habitual (7.8 +/- 0.7-hour) bedtimes. The screening differe nces between the groups in average daily sleep latency were consistent ly seen on the two further baseline nights and days. The extension of bedtime in sleepy subjects was followed by an increase in average dail y sleep latency relative to randomly chosen sleepy subjects maintained on their habitual sleep schedule for the 14 nights. The increase in a verage daily sleep latency was associated with a gradual reduction in sleep efficiency over the 14 nights. Some (36%) of the sleepy subjects did not have increased average sleep latencies during the 10-hour bed time extension. Those showing no increase in average daily sleep laten cy had an immediate drop in sleep efficiency when the bedtime was incr eased to 10 hours, suggesting they were unable to sleep longer during the extension. Their short average daily sleep latency was a result of causes other than chronic insufficient sleep.