Shift work causes misalignment between internal circadian time, and the external light-dark cycle and is associated with metabolic disorders and cancer. Approximately 20% of the working population in industrialized countries work permanent or rotating night shifts, exposing this large population to the risk of circadian misalignment-driven disease. Analysis of the impact of shift work on chronic inflammatory diseases is lacking. We investigated the association between shift work and asthma.
We describe the cross-sectional relationship between shift work and prevalent asthma in >280,000 UK Biobank participants, making adjustments for major confounding factors (smoking history, ethnicity, socio-economic status, physical activity, BMI). We also investigated chronotype.
Compared to day workers, ‘permanent’ night shift workers had a higher likelihood of moderate/severe asthma (odds ratio (OR) 1.36 (1.03-1.8)) and all asthma (OR 1.23 (1.03-1.46)). Individuals doing any type of shift work had higher adjusted odds of wheeze/whistling in the chest. Shift workers who never or rarely worked on nights and people working permanent nights had higher adjusted likelihood of having reduced lung function (FEV1 <80% predicted). We found an increase in moderate/severe asthma risk in morning chronotypes working irregular shifts, including nights (OR 1.55 (1.06-2.27).
Public health implications of these findings are far-reaching due to the high prevalence and co-occurrence of both asthma and shift work. Future longitudinal follow-up studies are needed to determine if modifying shift work schedules to take into account chronotype might present a public health measure to reduce the risk of developing inflammatory diseases, such as asthma.