Increased risk of asthma in female night shift workers

Rationale: Asthma is more common in females and more common in
night shift workers. Since increasing numbers of females are becoming
shift workers it is important to determine if shift work-associated asthma
risk is higher in females.

Objective: To determine if increasing frequency of shift work is more
strongly related to prevalent asthma in females than in males.

Method: We used cross-sectional data from >280,000 UK Biobank
participants and logistic regression models adjusted for demographic and
lifestyle factors to describe sex differences in prevalent asthma
phenotypes related to shift work frequency. To obtain mechanistic
insights, we explored associations with chronotype, sex hormones and
menopause.

Results: Compared to female day workers, female permanent night shift
workers had higher covariate-adjusted odds of moderate-severe asthma
(OR: 1.50 (95% CI 1.18 – 1.91)) but there was no corresponding
relationship in males (OR 0.95 (95% CI 0.72–1.26); sex interaction pvalue
= 0.01). Similar relationships were observed for ‘all asthma’ and for
‘wheeze or whistling in the chest’ outcomes. Female shift work-related
asthma was driven by relationships in postmenopausal women not using
HRT (e.g., adjusted OR: 1.89 (1.24-2.87) for moderate-severe asthma;
sex interaction p-value = 0.02 in permanent nightshift workers compared
to dayworkers) but these relationships attenuated to the null in
postmenopausal women using HRT.

Conclusion: Our finding that increasing shift work frequency is more
strongly related to asthma in females than in males could have Public
Health implications. Intervention studies should determine if modifying
shift work schedules or HRT can reduce asthma risk in females.