CHANGES IN PSYCHOPHYSIOLOGICAL FUNCTIONS DURING NIGHT-SHIFT IN NURSES- INFLUENCE OF CHANGING FROM A FULL-DAY TO A HALF-DAY WORK SHIFT BEFORE NIGHT DUTY
F. Kobayashi et al., CHANGES IN PSYCHOPHYSIOLOGICAL FUNCTIONS DURING NIGHT-SHIFT IN NURSES- INFLUENCE OF CHANGING FROM A FULL-DAY TO A HALF-DAY WORK SHIFT BEFORE NIGHT DUTY, International archives of occupational and environmental health, 69(2), 1997, pp. 83-90
The effects of changing from a full-day to a half-day shift work befor
e a night duty shift on physiological and psychological functions duri
ng the night shift were investigated in 12 healthy unmarried nurses wo
rking on the same ward of a university hospital. Three shift patterns,
i.e., a day shift following a day shift, a night shift following a da
y shift, and a night shift following a half-day shift, were studied in
terms of physical activity level, sympathetic and parasympathetic act
ivity levels, cortisol, prolactin, NK cell activity, and changes in mo
od states. The change to the half-day shift increased the duration of
sleep before night duty by about 86 min and brought wake-up times forw
ard by about 1 h, resulting in increases in rest and time before work.
In addition, the change was revealed to reduce the influence of rever
sed-phase circadian rhythms on autonomic nervous activity during the n
ight shift. The score for sleepiness was significantly lower at 0500 h
ours following a half-day shift. There were some marginal but not sign
ificant differences in the scores reflecting the degree of vigor, tire
dness and irritation during the night shift. Although the prolactin co
ncentration was significantly decreased at the start of the night shif
t after the half-day shift, there was no difference in cortisol concen
tration or NK cell activity between the usual night shift after a day
shift and the night shift after the half-day shift. The half-day shift
was not observed to cause any marked change in the fixed biorhythms o
f these nurses. The cortisol and NK cell activity levels were low duri
ng the night shift, suggesting that the night shift itself is a high s
tress level, which is prejudicial to biodefense.