This is the first large-scale research to evaluate sex differences in the relationship between night shift work and asthma severity
Women who work night shifts may face a significantly higher risk of developing moderate to severe asthma, according to a new study involving more than 270,000 people. The research, published in ERJ Open Research, found no such link in men, highlighting a potential gender difference in how night work affects respiratory health.
The study found that women working permanent night shifts were about 50 per cent more likely to suffer from moderate or severe asthma compared to those working regular daytime hours. Researchers believe the disruption to the body’s internal clock—or circadian rhythm—may be a contributing factor.
“Asthma disproportionately affects women. They generally experience more severe symptoms and higher rates of hospitalisation and death from asthma than men,” explained Dr. Robert Maidstone from the University of Manchester, UK, who led the study.
This is the first large-scale research to evaluate sex differences in the relationship between night shift work and asthma severity. The findings expand on previous research linking night shifts to increased asthma risk but now suggest the effect may be gender-specific.
The study analysed data from 274,541 working adults and found that 5.3 per cent had asthma, with 1.9 per cent experiencing moderate to severe forms—characterised by the use of preventer inhalers along with additional treatments like oral steroids.
Interestingly, postmenopausal women not taking hormone replacement therapy (HRT) showed almost double the risk of moderate or severe asthma if they worked night shifts, compared to daytime workers. This has raised new questions about the potential protective role of female hormones in asthma risk.
Researchers suggest that lower testosterone levels—more common in women—might make them more vulnerable, as testosterone has previously been shown to have protective effects against asthma. Alternatively, the difference may be due to men and women working in different shift environments.
“Our results suggest that HRT might be protective against asthma in nightshift workers, but more research is needed to test this theory in clinical trials,” said Dr. Maidstone. The team now plans to explore whether sex hormones directly influence the link between shift work and asthma.
As shift work becomes increasingly common, especially in sectors like healthcare, hospitality and manufacturing, this study underscores the need to better understand how work patterns affect long-term respiratory health—particularly for women.
