Marvin OnumonuWomen working night shifts are more likely to have asthma, according to a study by the University of Manchester published in ERJ Open Research.
The research used data from the UK Biobank, looking at 274,541 workers and showed women working night shifts had a higher risk of moderate or severe asthma compared to women working only in the daytime.
Of those, 5.3% had asthma and 1.9% had moderate or severe asthma, defined as people taking a preventer inhaler and at least one other asthma treatment.
Workers were grouped by those who worked only days, only nights, or a mix.
There was no link between night shifts and asthma in men.
Dr Robert Maidstone from the University of Manchester said: “Asthma disproportionately affects women.
“Women generally have more severe asthma, and higher rate of hospitalisation and death from asthma compared to men.
“In our previous research we found a higher risk of moderate or severe asthma in nightshift workers, so we wanted to see whether there were further differences between the sexes.”
Dr Maidstone added: “This is the first study to evaluate sex differences in the relationship between shift work and asthma.
“We found that permanent night shift-workers had higher odds of moderate-severe asthma when compared to corresponding day workers.”
He said: “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.”
In postmenopausal women, night workers not taking hormone replacement therapy (HRT) were almost twice as likely to have moderate or severe asthma compared to day workers.
Dr Maidstone said: “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 team plans to look further into whether sex hormones play a role by using more data from the UK Biobank and the Our Future Health programme.
Professor Florence Schleich from the European Respiratory Society’s expert group on airway diseases, asthma, COPD and chronic cough at the University of Liège, said: “Asthma is a common, long- term condition that affects millions of people worldwide.
“We know that women are more likely to have asthma, to have worse asthma and more likely to die from asthma, but we do not fully understand why.
“This research suggests that working nightshifts could be a risk factor for asthma in women, but not in men.
“The majority of workers will not have an easy option of switching their shift pattern, so we need further research to verify and understand this link and find out what could be done to reduce the risk for women who work shifts.”
