Homeostatic sleep regulation in habitual short sleepers and long sleepers.

Homeostatic sleep regulation in habitual short sleepers (sleep episode < 6 h, n = 9) and long sleepers (> 9 h, n = 7) was investigated by studying their sleep structure and sleep electroencephalogram (EEG) during baseline conditions and after prolonging their habitual waking time by 24 h. In each sleep episode, total sleep time was > 3 h longer in the long sleepers than in the short sleepers. Sleep deprivation decreased sleep latency and rapid eye movement (REM) density in REM sleep more in long sleepers than in short sleepers. The enhancement of EEG slow-wave activity (SWA; spectral power density in the 0.75-4.5 Hz range) in non-REM sleep after sleep loss was larger in long sleepers (47%) than in short sleepers (19%). This difference in the SWA response was predicted by the two-process model of sleep regulation on the basis of the different sleep durations. The results indicate that short sleepers live under a higher "non-REM sleep pressure" than long sleepers. However, the two groups do not differ with respect to the homeostatic sleep regulatory mechanisms.