Greer Bryden

Bio: Greer Bryden is an academic researcher from University of the Witwatersrand. The author has contributed to research in topics: Nap & Slow-wave sleep. The author has an hindex of 1, co-authored 1 publications receiving 51 citations.

Effects of night duty on sleep patterns of nurses

Abstract: The diurnal sleep patterns of female nurses working night duty were compared to their nocturnal sleep patterns while they were working regular hours during the day. Continuous EEG, EOG, and EMG recordings were made at the end of 2 month periods of night and day duty respectively. Day and night sleep differed with respect to both duration and pattern. Despite an earlier onset, the major sleep period was shorter during the day than the night and seemed to be more interrupted later in the session. This finding is in keeping with the increased amount of Stage 1 and decreased amount of slow wave sleep during the day than the night. Although no differences were evident with respect to overall percent REM, differences in the distribution of REM did occur. REM sleep occurred sooner during day than night sleep and there was more of it during the first part of day sleep. Thus night duty seemed to affect the pattern of sleep stage distribution as well as the absolute amount of, not only total sleep, but also some sleep stages, such as Stage SS. It is an open question how the naps of extended duration taken while on night duty influence the pattern of sleep during the day.

Work hours, sleepiness and the underlying mechanisms.

Abstract: Severe subjective and physiological sleepiness occur in night work, afflict almost all individuals and are associated with a performance impairment severe enough to explain night-work accident data. The alertness deficit is caused by the displacement of work to the circadian phase which is least conducive to alert behaviour, by extension of the time spent awake and by the reduction of sleep length (due to circadian interference with sleep). Sleepiness will be extreme when the three causes are operative simultaneously. The three factors may be used quantitatively to predict sleepiness.

The sleep and performance of shift workers.

Abstract: The sleep and performance of 12 male shift workers, operating a discontinuous, weekly alternating, three-shift system, were monitored over the course of one complete shift cycle. Compared with noct...

Distribution of REM sleep in entrained 24 hour and free-running sleep--wake cycles.

Abstract: One hundred thirty sleep episodes of 6 subjects, living on a natural 24 hr day, were compared with 116 sleep times of the same subjects living isolated from external time cues The polygraphic sleep recordings were analyzed for the distribution of REM sleep under both conditions Additionally, the relationship between body temperature and REM sleep was analyzed by comparing sleep episodes in which the temperature minimum occurred early in the sleep episode with those in which there was a late temperature minimum The results show that there is more REM sleep in the beginning of sleep in sleep episodes of free-running rhythms as compared to sleep episodes of entrained 24 hr rhythms This higher amount of REM sleep is due to a longer first REM episode and shorter first NREM episodes The comparison of the sleep episodes that differ in the position of the temperature minimum shows similar differences, ie, more REM sleep in the beginning of sleep episodes in which the temperature minimum occurs earlier as compared to episodes in which the temperature minimum occurs later It was hypothesized that the amount of REM sleep depends on the phase relationship between sleep and the circadian temperature cycle From this point of view, the difference in the distribution of REM sleep in the entrained 24 hr rhythm, on the one hand, and the free-running rhythm, on the other hand, can be explained by the different courses of body temperature during sleep That only the first REM episode is influenced by circadian parameters may indicate an exceptional role for this REM episode in contrast to the following episodes