Individual Variations in Awakening Times, Daytime Alertness and Somnograms as a Function ofAd LibitumExtended Sleep

Abstract

Individual variations in timing of polysomnograms, vigilance, alertness ratings and wakeful electrocorticograms were investigated after being potentiated by extended sleep. The entire (n = 16) constituency of healthy young adults was dichotomized into subgroups (Ns = 8) whose delayed awakenings occurred before 1045 (0930-1036) h and at 1105 (1105-1430) h or later. Statistical analyses were applied to determine whether selected dependent variables during ad lib delayed sleep covaried as a function of the substantial (5-h) range observed for awakening times. Relative to the rigidly scheduled 8-h control condition, statistically significant average increases occurred in stage 2, REM [rapid eye movement] sleep and REM cycle length as a function of delayed afternoon awakening times, whereas this proved true for stage 3 during the morning. For all indexes of sleep physiology, there were statistically significant interactions of the ad-lib extended treatment with arising times. Average elevations in stage 2, REM sleep and REM cycle length were associated with ad lib sleep which terminated at 1105 h or later. Increases of stage 3 coincided with extended sleep wherein awakenings occurred between 0930 and 1036 h in the morning. The average integrated amplitude (.mu.V) of 8-13 Hz .alpha. rhythm was greater (less cortical alertness), whereas psychometric alertness ratings were significantly less in conjunction with ad lib delayed morning sleep and among individuals whose awakenings occurred > 1100 h. Sublingual temperature was significant lymore elevated within the vicinity of 1105-1430 and this proved true with respect to d, the signal detection index, from 0930 until 1036 h. Accumulated evidence does indicate that acute variations in sleep patterns contribute to a disturbance in the diurnal cycle most conspicuously during either: morning or when postdormital evaluations of alertness are initially completed. The clinical relevance of these findings for neuropsychiatric states such as idiopathic hypersomnias, bipolar affective illness and depression is explicated.