Women who work night shifts more likely to have asthma

Women who work night shifts are more than fifty per cent more likely to suffer from moderate or severe asthma than women who work during the day, a new study has suggested.

Researchers from the University of Manchester analysed data from nearly 270,000 shift workers and found that for all women working night shifts, the risk of asthma increased. The risk was more pronounced in women who only worked nights and in postmenopausal women who were not taking hormone replacement therapy (HRT). There was no association between working night shifts and asthma in men.

The findings, published in ERJ Open Research, highlight the need for women working night shifts to monitor their health.

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Women working night shifts around 50 per cent more likely to suffer from moderate or severe asthma

Using data from the UK Biobank, the researchers analysed data from 274,541 working people. Participants were categorised as day or night workers, or a combination of both, and statistical analysis was applied to determine how the increasing frequency of shift work affects asthma risk. To determine possible causes of any association, chronotype, sex hormones, and menopausal information were also analysed and demographic and lifestyle factors were controlled for.

Of the people analysed in the study, 5.3 per cent had asthma, with 1.9 per cent suffering from moderate or severe asthma, meaning they were taking an asthma preventer inhaler and at least one other asthma treatment, such as an oral steroid.

The findings show that women who work shifts are more likely to have asthma. Women who only work night shifts are around 50 per cent more likely to suffer from moderate or severe asthma compared to women who only work in the daytime.

No association between working night shifts and asthma in men

There was no significant link between night shift work and asthma risk found in men, suggesting that biological sex, linked to either hormonal or physiological differences, plays a role in how night shift work affects a person’s asthma risk.

Dr Robert Maidstone, from the University of Manchester and lead researcher on the study, said: ‘This is the first study to evaluate sex differences in the relationship between shift work and asthma. This type of research cannot explain why shift work and asthma are linked; however, it could be because shift work disrupts the body clock, including the levels of male and female sex hormones. High testosterone has previously been shown to be protective against asthma, and so lower testosterone in women could play a role. Alternatively, men and women work different types of shift jobs, and this could be a factor.’

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Examining the impact of the menopause and associated HRT, the researchers found that women who are postmenopausal and not using HRT have nearly double the odds of severe asthma compared to day workers. Among postmenopausal women working night shifts, those using HRT did not exhibit the same elevated asthma risk.

Dr Maidstone added: ‘Our results suggest that HRT might be protective against asthma for nightshift workers, however further research is needed to test this hypothesis in prospective studies and randomised controlled trials.’

The group plans to examine whether sex hormones play a role in the relationship between shift work and asthma in future research.

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Reference: RJ Maidstone, DW Ray, Junxi Lui, et al. Increased risk of asthma in female night shift workers. ERJ Open Research 2025 00137-2025; DOI: https://doi.org/10.1183/23120541.00137-2025