Behavioral and psychophysiological correlates of irregularity in chronic sleep routines

Behavioral and psychophysiological correlates of irregularity in chronic sleep routines were studied. Two groups each of 18 healthy male university students were classified as either irregular sleepers or control subjects according to retrospective questionnaires, and sleep chart criteria. The control group was composed of persons who slept naturally from 12-8:00 a.m. for 7-8 hr. Irregular sleepers were defined as those whose retiring and awakening times varied by about 2-4 hr. Measurements were obtained from an auditory reaction time task, a mood adjective check list, of sublingual temperature and pulse rate 30 min. after awakening in the (a) morning, at (b) noon, in the (c) afternoon and (d) early evening following an electroencephalographically recorded 12-8:00 a.m. sleep night. At various points in the diurnal cycle irregular sleepers compared with the control group had significantly lower levels of pulse rate and body temperature, but significantly longer reaction times. During the four time periods negative affects (deactivation-sleep, depression, general deactivation, inert-fatigued) were significantly greater and positive mood states (cheerful, energetic, general activation--significantly less in the irregular sleepers. The irregular sleepers averaged significantly less stage 4, and REM, but more stage 2 and transitions between sleep stages. The present results indicate that relatively lowered levels of physiological arousal indexes, psychomotor performance and subjective mood are associated with irregularity in chronic sleep routines of young adult males. These psychobehavioral correlates of chronically maintained sleep pattern variations complement and extend previous findings on degradations in waking functions following acute 2-4 hr temporal shifts of habitual sleep periods. It is postulated that there were psychobehavioral deficits in the irregular sleepers attributable either to selective sleep stage (REM and/or stage 4) deprivation or to the more general consequence of disturbed sleeping patterns per se or to both of these factors.