Shift work linked to asthma

3 minute read

The effect is worst in extreme chronotypes – owls/larks – and appears to relate to disrupted circadian rhythms.

Really, who would do shift work?

Researchers have now discovered that working night shifts not only increases the risk of cardiovascular disease, metabolic disorders and cancer (which we knew already), but also appears to increase the risk of moderate to severe asthma.

To examine the potential relationship between asthma and shift work, the UK researchers analysed the medical, lifestyle and employment information on over 280,000 adults, aged 37 to 72 years who were participants in the UK Biobank from 2007 to 2010.

What they found, after adjusting for a whole range of possible confounders, was that shift work, in particular consistent night shifts was associated with significant asthma.

“This study shows that, compared with day workers … people working permanent nights had higher adjusted odds of moderate- severe asthma [and] people doing any type of shift work had higher adjusted odds of wheeze or whistling in the chest,” the researchers wrote in the journal, Thorax.

And why would night shift work be associated with asthma, you may ask?

Well, according to the study authors, it all relates to disruption of the body’s normal circadian rhythms.

“Shift workers, especially those working night shifts, sleep at an inappropriate circadian phase, causing circadian misalignment between their sleep/wake behaviour and endogenous circadian processes,” they said. And according to animal studies, at least, it’s this circadian misalignment that can lead to the development of asthma.

To investigate this theory further, the researchers looked at the “chronotype” of the participants, which means they determined whether a person was a night person (an owl) or a morning person (a lark), and whether this had any bearing on the incidence of asthma.

It appears, according to this study, it’s the degree to which a person is a night or morning person that matters, not so much whether you are an owl or a lark.

“We found that extreme chronotypes were significantly more likely to have asthma even after multivariable adjustments,” they said.

This supports the hypothesis that morbidity is associated with disruption to the circadian rhythm. People who function significantly better at certain times of the day, be it evening or morning, are obviously more susceptible to circadian rhythms, and therefore more affected by disruption to these.

Researchers went on to suggest how their findings could result in potentially better health outcomes for shift workers.

“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” they suggested.

It may be important to remember the prevalence of both shift work and asthma in the community. This study confirms what previous research had already suggested: that one in five of the employed adult population does shift work. And according to these researchers, the estimated prevalence of asthma in the UK is about 10%.

With these sort of figures, the study authors suggest the public health implications of this latest analysis are potentially quite significant.

This piece was originally published at

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