Evidence from the waking electroencephalogram that short sleepers live under higher homeostatic sleep pressure than long sleepers

We used the waking electroencephalogram to study the homeostatic sleep regu latory process in human short sleepers and long sleepers. After sleeping ac cording to their habitual schedule, nine short sleepers (sleep duration <6 h) and eight lung sleepers (>9 h) were recorded half-hourly during similar to 40 h of wakefulness in a constant routine protocol. Within the Frequency range of 0.25-20.0 Hz, spectral power density in the 5.25-9.0 and 17.25-18 .0 Hz ranges was higher in short sleepers than in long sleepers. In both gr oups, increasing time awake was associated with an increase of theta/low-fr equency alpha activity (5.25-9.0 Hz), whose kinetics followed a saturating exponential function. The time constant did not differ between groups and w as similar to the previously obtained time constant of the wake-dependent i ncrease of slow-wave activity (0.75-4.5 Hz) in the sleep electroencephalogr am. In addition, the time constant of the decrease of slow-wave activity du ring extended recovery sleep following the constant routine did not differ between groups. However, short sleepers showed an abiding enhancement of th eta/low-frequency alpha activity during wakefulness after recovery sleep th at was independent of the homeostatic process. It is concluded that, while the kinetics of the homeostatic process do not differ between the two groups, short sleepers live under and tolerate highe r homeostatic sleep pressure than long sleepers. The homeostat-independent enhancement of theta/ low-frequency alpha activity in the waking electroenc ephalogram in the short sleepers may he genetically determined or be the re sult of long-term adaptation to chronically short sleep. Published by Elsev ier Science Ltd.