Shift workers, especially those working permanent night-shift rotas, may be at heightened risk of moderate to severe asthma, suggests research published online in the journal Thorax.
The observational study, led by researchers at the University of Manchester, drew on medical, lifestyle and employment information supplied between 2007 and 2010 by 286,825 participants in the UK Biobank.
All participants were aged between 37 and 72 years, and either in paid employment or self-employed. Most (83%) worked regular office hours, while 17 per cent worked shifts, around half of which (51%) included night shifts. Shift patterns comprised: never or occasional night shifts; irregular or rotating night shifts; and permanent night shifts.
Compared with those working office hours, shift workers were more likely to be men, smokers and to live in urban areas and in more deprived neighbourhoods. They also drank less alcohol, slept fewer hours and worked longer hours.
Fourteen thousand two hundred and thirty-eight (5.3%) participants had asthma, 4783 (nearly 2%) of whom had moderate to severe asthma symptoms.
Compared with day workers, 'permanent' night shift workers had a higher likelihood of moderate-severe asthma (OR, 1.36; 95% CI, 1.03-1.8) and all asthma (OR, 1.23; 95% CI, 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 nights and people working permanent night shifts had a higher adjusted likelihood of having reduced lung function (forced expiratory volume 1
There was an increase in the risk of moderate-severe asthma in morning chronotypes working irregular shifts, including nights (OR, 1.55; 95% CI, 1.06-2.27).
Genetic susceptibility to asthma did not affect the odds of developing asthma among those working shifts.
The authors say it is plausible that circadian misalignment leads to asthma development.