Night shifts may affect women more than men: study

Researchers, including one of Indian-origin, have found that women may be more affected by night-shift work than men. The study found that shifted sleep-wake cycles affect men and women's brain function differently.

Researchers from University of Surrey in the UK 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 was monitored continuously during sleep. The results showed that in both men and women, self-reported assessments were more sensitive to the effects of time awake and circadian clock than the many



objective measures of performance, researchers said.

However, the circadian effect on performance was significantly stronger in women than in men such that women were more cognitively impaired during the early morning hours, which in the real world typically coincides with the end of a night shift.

"We show for the first time that challenging the circadian clock affects the performance of men and women differently," said Nayantara Santhi from University of Surrey.

"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," said Santhi.

"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," said Derk-Jan Dijk from University of Surrey.

The findings were published in the journal PNAS.