Sleep-wake cycles controlled by antisocial shifts affect men and women’s brain function differently, according to UK researchers.
They found the ability to perform tasks was more affected in women than in men, which the study authors noted could have “significant implications” for female nightshift workers such as nurses and police officers.
“Extrapolation of these results would suggest that women may be more affected by night-shift work than men”
The researchers, from the sleep research centre at Surrey University, placed 16 male and 18 female participants on 28-hour days in a controlled environment without natural light-dark cycles.
It effectively desynchronised the sleep-wake cycle from the brain’s 24-hour – circadian –clock, similar to jet lag or a shiftwork scenario, said the researchers in the journal Proceedings of the National Academy of Sciences.
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 – such as measures of attention, motor control and working memory.
Brain electric activity was monitored continuously during sleep. The results revealed 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.
However, crucially, the researchers found the circadian effect on performance was significantly stronger in women than in men, to the point 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.
Female nurses ‘more affected by nightshifts’ than men
Study co-author Dr Nayantara Santhi 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,” she said. “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.”