Men and women are affected differently when their natural sleep pattern is disrupted. A study looking at gender differences in sleep disruption found women tend to perform worse on tasks following night shift work. These included tasks involving memory, attention and motor control.

Previous studies have shown shift work, which affects the circadian rhythm – the natural body clock – can cause fatigue, bad moods and a lower cognitive function. However, most of this research was carried out on men. Whether sleep-wake cycles affects the brain function of men and women in different ways was not known.

Researchers from the University of Surrey used 16 male and 18 female volunteers to find differences in performance following night-shift work. They were kept in an environment without natural light (or natural darkness) for 10 consecutive 28-hour days; mimicking night-shift work.

While awake, the volunteers completed tiredness self-assessments and a series of tasks every three hours. These tasks included short tests of memory and attention. While asleep, their brain activity was monitored.

The findings, published in PNAS, showed that both men and women performed worse on tasks following a change to their body clock. However, these changes were significantly more pronounced in women, who struggled more on cognitive tests conducted at what would have been at the end of a night-shift.

Nayantara Santhi, co-author of the research, 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 shift work-related cognitive deficits and changes in mood. These results would suggest that women may be more affected by night-shift work than men."

Researchers say the findings may help explain why women report more workplace injuries when working night-shifts and highlight the need to establish gender differences in the effects of shift work. "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," said study author Derk-Jan Dijk.