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Shift workers, especially those who work permanently on the night shift, may be at increased risk for moderate to severe asthma, according to a study published online in the journal Thorax.

Given the prevalence of shift work and asthma in developed nations, the public health implications of these findings are potentially “far-reaching,” the researchers warn.

Around every fifth employee in industrialized countries works permanent or rotating night shifts. Shift work results in a person’s internal clock (circadian rhythm) inconsistent with the external light and dark cycle.

This misalignment is linked to an increased risk of various metabolic disorders, cardiovascular diseases, and cancer.

Asthma symptoms such as wheezing and airway whistling vary significantly depending on the time of day or night, and the researchers wanted to find out whether shift work may also be linked to an increased risk of asthma and / or its severity.

They also wanted to investigate how influential the chronotype – the preference of the individual body clock for activities in the morning (“lark”) or in the evening (“owl”) – and the genetic predisposition for asthma could be.

They were based on medical, lifestyle and employment information provided between 2007 and 2010 by 286,825 participants in the UK biobank.

All of these participants were between 37 and 72 years old and either employed or self-employed. Most (83%) worked during regular office hours while 17% worked shifts, of which about half (51%) were night shifts. Shift patterns included: never or occasionally night shifts; irregular or rotating night shifts; and permanent night shifts.

Compared to these office hours, shift workers were more likely to be men, smokers and to live in urban areas and in deprived neighborhoods. They also drank less alcohol, slept fewer hours, and worked longer.

Night shift workers were more likely to be “owls” and in poorer health. And they worked more in service professions or as process, plant and machine operators. These working hours were usually in administrative functions and had professional jobs.

About 14,238 (around 5%) of all study participants had asthma; In 4,783 (nearly 2%), symptoms were moderate to severe (based on their medications).

The researchers compared the effects of working hours with shift work on the diagnosis of asthma, lung function and symptoms of asthma.

After considering age, gender and a variety of other potentially influential risk factors, the likelihood of moderate to severe asthma among permanent night shift workers increased by 36% compared to normal office hours.

Similarly, those who worked on any of the three shift patterns were 11 to 18% more likely to have wheezing or airway whistling, while shift workers who never or rarely worked at night and workers were about 20% more likely to have poor lung function % higher was permanent night shifts.

Those who were definitely either larks or owls known as “extreme chronotypes” had significantly more asthma, even when a number of potentially influential risk factors were considered. And the likelihood of moderate to severe asthma was 55% higher in larks who worked irregular shifts, including nights.

However, genetic susceptibility to asthma did not affect the likelihood of developing asthma during these work shifts.

This is an observational study so cannot determine a cause, say the researchers. “However, it is plausible that circadian misalignment leads to the development of asthma,” they point out.

“Interestingly, the chronotype changes with age, later in adolescence and then earlier in adulthood, suggesting that older people may find it harder to adjust to night shifts than younger adults,” they explain.

“The public health implications of our results are potentially far-reaching, as both shift work and asthma are common in the industrialized world,” they warn. Asthma affects 339 million people worldwide and costs health and care services more than £ 1 billion in the UK alone.

“There are no specific national clinical guidelines for the management of asthma in shiftworkers,” they point out, but adapting shiftwork schedules to the individual chronotype could be a worthwhile public health measure worth further study.

The researchers identify how night shift work creates confusion in the internal clock

More information:
Night shift work is associated with an increased risk of asthma, Thorax (2020). DOI: 10.1136 / thoraxjnl-2020-215218 Provided by the British Medical Journal

Quote: Permanent night shift workers with an increased risk of moderate to severe asthma (2020, November 16) have November 16, 2020 from retrieved

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