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Night shifts which disturb normal sleep-wake patterns affect women’s brain function more than men’s, according to a study from the Surrey Sleep Research Centre at the University of Surrey.
Researchers placed 16 male and 18 female participants on 28-hour days in a controlled environment without natural light-dark cycles. This effectively desynchronised the sleep-wake cycle from the brain’s 24-hour (circadian) clock, similar to jet lag or a shiftwork scenario.
Every three hours during the awake period, participants performed a wide range of tests, including self-reported assessments of sleepiness, mood and effort, and objective tests of cognitive performance which included measures of attention, motor control and working memory. Brain electric activity (EEG) was monitored continuously during sleep. The results revealed that both men and women’s performance was affected, but that the circadian effect on performance was significantly stronger in women than in men with women being more cognitively impaired during the early morning hours. This would typically coincide with the end of a night shift.
Co-author, Dr Nayantara Santhi from the University of Surrey, said: “We show for the first time that challenging the circadian clock affects the performance of men and women differently. Our research findings are significant in view of shiftwork-related cognitive deficits and changes in mood. Extrapolation of these results would suggest that women may be more affected by night-shift work than men.”
Senior author, Professor Derk-Jan Dijk, added: “These results show that in both men and women circadian rhythmicity affects brain function and that these effects differ between the sexes in a quantitative manner for some measures of brain function.”
The results are published in the Proceedings of the National Academy of Sciences journal.