The sleep of healthy people - A diary study

To provide baseline data for various research studies at the University of Pittsburgh over a 10-year period, 266 healthy subjects (144 male, 122 femal e, aged 20-50 years) meeting certain criteria each completed a 14-night sle ep diary. For each night, the diary allowed the subjective measurement of b edtime, wake time, time in bed (TIB), sleep efficiency, number of minutes o f wake after sleep onset (WASO), alertness on awakening, and percentage of mornings needing an alarm (or a person functioning as one). Weeknight versu s weekend night differences in TIE (TIBdiff), weekday alertness, and relian ce on alarms were examined as possible indicators of sleep debt. In additio n, general descriptive data were tabulated. On average, bedtimes were at 23 :48 and wake times at 07:23, yielding a mean TIE of 7 hours 35 minutes. As expected, bedtimes and wake times were later on weekend nights than on week nights. Bedtimes were 26 minutes later, wake times 53 minutes later, yieldi ng a mean weekend TIE increase of 27 minutes. Overall, subjects perceived t heir sleep latency to be 10.5 minutes, reported an average of one awakening during the night (with an average of 6.4 minutes of WASO), had a diary sle ep efficiency of 96.3%, and awoke with an alertness rating of 69.5%. These variables differed little between weeknight and weekend nights. Subjects us ed an alarm (or a person functioning as an alarm) on 60.9% nights overall, 68.3% on weeknights, 42.5% on weekends. When TIBdiff was used as an estimat e of sleep debt (comparing subjects with TIBdiff > 75 minutes with those wi th a TIBdiff < 30 minutes), the group with more "catch-up sleep" on weekend s had shorter weeknight TIE durations (by about 24 minutes) and relied more on an alarm for weekday waking (by about 22%), indicating the possible uti lity of these variables as sleep debt indices.