Psychobiology and Pathologies of Human Sleep

Sleep pattern variations as a function of age in affective disorders

Polygraphic features of nocturnal sleep were evaluated in young adult psychiatric patients during acute unipolar depressive episodes. Averaged values and variability of polygraphic indexes were examined in 12 depressed patients under the age of 26 individually matched with a normal control group. Sleep was polygraphically recorded in the Laboratory for three consecutive nights from 12-8.00 a.m. Although average total time asleep was approximately equivalent (greater than 7.3 hr) between groups, depressives accumulated significantly: (i) less stage 4, (ii) more stage 1, (iii) vascillations among sleep stages, but (iv) most especially increased transitions into stage 1 and (v) intermittent wakefulness. The recorded sleep perturbations in young depressives were extremely variable across nights and among individuals. This was especially conspicuous across nights as reflected by significantly larger variability (SD) for: (i) transitions into stage 1, (ii) intermittent wakefulness and (iii) epsilon accumulations of stage 2. Variability (the SD) between individuals was also more substantial for: (i) total time asleep, (ii) stage 1, (iii) intermittent wakefulness, (iv) epsilon stage shifts and (v) intrusions into stage 1. The polygraphic recordings of young depressives contained anomalies reported for clinical pathologic states accompanied by physiological disregulation such as hypersomnia, narcolepsy and schizoaffective disorders. Polygraphic indexes reflecting the capacity (i) to remain asleep (means +/- SDs) and (ii) accumulate continuous sleep (SDs) indicated an imbalance of the 24-hr rest (sleep)--activity (waking) cycle was present in this constituency concomitant with affective distress. A comparison with selected cross-sectional polygraphic studies revealed that sleep cycle aberrations in young adult depressives were less intense than those which become exacerbated as a function of advanced age. By contrast to prepubertal children or postadolescent young adults who are depressed, elderly accumulate: (i) lower total sleep times, (ii) less proportions of stages 3-4 and (iii) remain awake longer. It is concluded that sleep-polygraphic anomalies in postadolescent depression are an attenuated form of the REM-NREM cycle perturabation endemic to affective disease occurring with advanced age or senescence.

Nocturnal electrographic features of frequently changing-irregular sleep-wakefulness rhythms

Polygraphic characteristics of nocturnal sleep associated with frequently changing-irregular rest-activity schedules were investigated in healthy young adults. Two groups each of 12 male university students were classified according to a priori criteria as either: (a) controls who slept regularly for 7--8 hr at night or (b) whose retiring and arising times combined varied chronically +/- 1.5 hr. Sleep was recorded during three consecutive 8-hr nocturnal periods at fixed clock times. Polygraphic indices generally reflected greater discontinuity and fragmentation associated with the nocturnal sleep in the young adults whose 24-hr rest-activity cycle tended to be frequently changing-irregular. The significantly: (a) larger absolute quantities of (i) transitional stage 1 sleep, (ii) intermittent wakefulness and (b) increases stage shifts provided some indication that the intrasleep cycle becomes disturbed when rest-activity schedules follow no predictable pattern in the everyday environment. Despite, or because of, the enforced hour (11:30 p.m +/- 30 min) for retiring, it is possible that the capacity to fall asleep had become phase-delayed among subjects with irregular rest-activity schedules who experienced more initial wakefulness (on average) before sleep onset stage 1. Finally, the recorded sleep perturbations associated with frequently changing-irregular schedules were extremely variable across nights and among individuals. This was especially pronounced on a nightly basis as reflected by significantly larger variability (SDs): (a) in the latency to sleep onset, for (b) total time asleep, (c) intermittent wakefulness, and (d) the ultradian (90-min) REM cycle. Variability (the SD) between individuals was also more substantial for these same polygraphic measures at statistically significant levels.