You know that feeling after a late night when things feel a bit out of whack? That’s your circadian clock – your body's inner timepiece – falling out of rhythm as it grapples with the fact you are awake when you should be asleep. Scientists have a specific name for this: ‘circadian misalignment’.

But not everyone suffers in the same way from this effect. A new study has suggested that women are more resilient than men to the damage a circadian misalignment can cause.

The findings “may have broad societal implications, from the design of shiftwork schedules to the capacity to cope with trans-meridian travel [travel across timelines],” says first author Seán Anderson, researcher from the Perelman School of Medicine at the University of Pennsylvania.

The new study, published in the journal Science Translational Medicine, analysed health data from over 92,000 people with a history of shiftwork (work that takes place outside the hours of 7am – 6pm on a fixed or rotating basis). It found that both men and women have a higher incidence of metabolic syndrome when working shifts – but that the risk is significantly higher for male shift workers than for women doing the same job. Female shift workers were also found to sleep better than their male counterparts.

Intriguingly, these findings are similar to findings in mice. As part of the same study, the scientists exposed the animals (who were fed a high-fat diet) to abnormal day-night cycles. While the microbiomes, metabolism, and behaviour of the female mice were largely unaffected by the conditions, male mice demonstrated higher blood pressure and shifts in their gut microbiome and liver metabolism. The scientists also found that the male mice gained substantially more weight after 12 weeks of biweekly ‘shifts’ than the female mice.

The circadian clock runs on a 24-hour cycle from our brains, and controls clocks in organs around our bodies. Though best known for controlling our sleep schedule, the rhythms of these clocks direct all aspects of our physiology, from deciding the function of cells to governing our metabolism.

Previous studies have shown shiftwork can cause issues to health and sleep, such as metabolic syndrome (a cluster of conditions including high blood pressure and blood sugar levels that increase the risk of heart disease and stroke) and accidents at work.

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Noa LeachNews editor, BBC Science Focus

Noa Leach is the News editor at BBC Science Focus. With an MPhil degree in Criticism & Culture from the University of Cambridge, Noa has studied cultural responses to the climate crisis, wildlife, and toxicity. Before joining BBC Science Focus, Noa was the Editor of The Wildlife Trust BCN’s magazine Local Wildlife. Her writing has been shortlisted for the Future Places Environmental Essay Prize.