Asthma is a chronic respiratory disease that is influenced by both genetic and environmental factors, and it is more prevalent in women who work night shifts. As many women work in shifts, it is important to determine whether women are more susceptible to asthma symptoms related to shift schedules. Previous population studies have suggested a link between night shift work and asthma; however, it remains unclear whether this association holds for both women and men.
The UK Biobank is a large population-based dataset used in this study to examine sex-specific associations between shift work and asthma. Previous research shows that “permanent” night shift workers were more likely to have moderate-to-severe asthma than day workers, using data from over 280,000 UK Biobank participants.
The increased incidence of asthma in girls starts during puberty and is linked to hormonal changes during menstruation, pregnancy, and menopause. This indicates that female sex hormones play an important role in the development of asthma. The study utilized cross-sectional data from 274,541 individuals in the UK Biobank, who were either employed or self-employed.
A combination of self-reported medical diagnosis and medication was used to classify cases of asthma and moderate-to-severe asthma. The referent group was defined as oestradiol levels below the reportable limit of 175 pmol/L. Measurements that fell outside the reportable range were assigned to the cut-off value in the continuous analysis.
Multivariable-adjusted logistic regression models were used for day workers as the referent group to estimate odds ratios (OR). After multivariate adjustment, female permanent night shift workers were more likely than their day shift colleagues to have moderate to severe asthma [OR=1.50; 95% confidence interval (CI): 1.18–1.91]. There was a sex-based interaction for the probability of having asthma symptoms, with women working shifts showing a higher correlation as compared to men. These associations were caused by postmenopausal women who did not undergo hormone replacement therapy (HRT). These women had a 1.9 times higher risk of developing asthma if they worked night shifts regularly.
To explore more about menopausal status as the primary cause of the sex effect, researchers investigated the interaction between sex and shift work. Asthma was negatively correlated with serum testosterone and sex-hormone binding globulin in both genders. Greater testosterone levels did not reduce the sex-specific associations with night shift work when included in multivariate models.
The primary conclusion was that working night shifts increases the risk of developing moderate-to-severe asthma in women, but not in men. For permanent night shift workers, this link was stronger, and lifestyle factors, chronotype, and sex hormones were not found to be responsible for it. For both “any asthma” and “wheeze” outcomes, the study also discovered an interaction between sex and shift employment.
Future workplace regulations, physician awareness campaigns, and other interventions may help reduce the risk of asthma in women, particularly those who work permanent night shifts. Further randomized controlled trials are required to determine whether HRT may offer protection to postmenopausal shift workers from asthma. There could be major health and economic advantages if it were possible to decrease the risk of asthma in women by changing work schedules or starting HRT at menopause.
Reference: Maidstone RJ, Ray DW, Liu J, et al. Increased risk of asthma in female night shift workers. ERJ Open Res. 2025. DOI:10.1183/23120541.00137-2025
