Women who work night shifts could be more affected by disrupted sleep than men, new research suggests.
Experts said the results have "significant implications" for female night shift staff such as nurses, security guards and police officers.
They explained that while both sexes were affected by lack of sleep, women's performance suffered the most.
Previous studies have linked shift work with depression and increased risk of workplace injury.
Shift work has been known to affect sleep. In fact, a study of police officers found that those on the night shift got, on average, fewer than six hours sleep a night.
Sleep is a requirement, just like food, and long-term health outcomes from not getting enough of it include obesity, Type 2 diabetes, cardiovascular diseases and high blood pressure.
Researchers from the University of Surrey placed 16 male and 18 female participants on 28-hour days in a controlled environment without natural light-dark cycles.
This desynchronised the sleep-wake cycle from the brain’s 24-hour (circadian) clock, in a similar way to jet lag or night shifts.
They discovered that shifted sleep-wake cycles affect men and women’s brain function differently.
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.
During sleep, brain electric activity (EEG) was monitored continuously.
The results revealed that the effect on performance was significantly stronger in women than in men.
Women were also more cognitively impaired during the early morning hours, which would typically coincide with the end of a night shift.
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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 continued: "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.
"Overall the findings illustrate how important it is to include both men and women in research studies and to use a wide range of subjective and objective indicators of brain function."
The study was published in the journal PNAS (Proceedings of the National Academy of Sciences).