Plasma growth hormone and slow wave sleep increase after interruption of sleep

A comparison was made of plasma hGH and of sleep stages during one night of undistrubed sleep and one night in which sleep was interupted by an hour of enforced wakefulness folowing the end of the second NREM-REM sleep cycle in 8 normal subjects. Plasma was sampled at 15-min intervals. HGH and slow wave sleep were both significantly increased in the two cycles immediately following the period awake compared with the same two cycles during nights of uninterruped sleep. The difference arose predominantly in the fourth cycle of the night, i.e., in the second cycle after the sleep interuption. The findings are consistent with the belief that extra wakefulness brings additional sleep of high RESTORATIVE properties.