title: Stage 4 sleep: influence of time course variables.
abstract: Age, length of prior wakefulness, length of time asleep, and a circadian influence all affect stage 4 sleep. The amount of stage 4 sleep decreases as subject's age increases and as time asleep increases. Longer periods of wakefulness before sleep result in greater amounts of stage 4 sleep in the first 3 hours of sleep. Sleep periods that begin at times other than the regular onset time tend to produce less stage 4 sleep; this decrease suggests a circadian effect.
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D002648:Child; D002675:Child, Preschool; D002940:Circadian Rhythm; D004569:Electroencephalography; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D012894:Sleep Stages; D013997:Time Factors; D014851:Wakefulness