Decoding the findings of a study linking night shifts with asthma problems in women

The Hindu

27-06-2025

A recent study has found a correlation between working night shifts and asthma, especially in women.
The study, 'Increased risk of asthma in female night shift workers' published in ERJ Open Research, based its findings on cross-sectional data from over 2,80,000 U.K. Biobank participants.
The study builds on previous research that had found a higher risk of moderate or severe asthma in night shift employees. Researchers found that 5.3 per cent of the workers had asthma, with 1.9 per cent suffering from moderate or severe asthma (taking an asthma-preventer inhaler and at least one other asthma treatment, such as an oral steroid).
The study's findings
Led by Robert Maidstone of the University of Manchester, U.K., the study found that women who worked night shifts were more prone to moderate to severe asthma. Women who only worked night shifts were found to be around 50 per cent more likely to suffer from moderate or severe asthma compared to women who only worked in the daytime. Although it has been established that more adult women than men are prone to asthma the reason for this has been elusive.
The researchers believe that testosterone, the male sex hormone, has a protective effect that prevents asthma triggers in men, and suggested that post-menopausal women could opt for hormone replacement therapy as it appears to have a protective effect.
What is asthma?
Asthma is a major noncommunicable disease (NCD), affecting both children and adults, and is the most common chronic disease among children.
Inflammation and narrowing of the small airways in the lungs cause asthma symptoms, which can be any combination of cough, wheeze, shortness of breath and chest tightness.
Inhaled medication can control asthma symptoms and allow people with asthma to lead a normal, active life.
Avoiding asthma triggers can also help to reduce asthma symptoms.
Asthma is often under-diagnosed and under-treated, particularly in low- and middle-income countries. Source: WHO
R. Sridharan, a Chennai-based specialist in treating allergies, concurs with the findings of the study. He explains that our body is regulated by the circadian rhythm (the internal clock managing the sleep-wake process). When a person's circadian rhythm changes as in the case of those working night shifts, they end up suffering from a number of health issues which could include acid reflux, gastro-oesophageal reflux disease (GERD), obesity, obstructive sleep apnoea, besides hormonal changes. This can have a number of effects including increasing the chances of getting asthma, Dr. Sridharan said.
While asthma can be triggered by allergies and pollution, obesity too, is linked with an increased risk of developing for asthma according to the United States National Heart, Lung, and Blood Institute. 'Obesity is common due to loss of normal sleep patterns,' said Dr. Sridharan, adding: 'What I am seeing is night duty people have more asthma and less controlled asthma and are prone for many asthma triggers,' he adds.
Allergies, he says, are linked to low levels of immunity, again caused by disruptions to sleep and inadequate sleep, which could then trigger asthma.
Dr. Sridharan however points out that as a specialist, of 30 patients in a day, he sees 25 with asthma, and both men and women and equally prone to the condition.
Pulmonologist M. Koushik Muthu Raja said he had treated a few persons who work night shifts and presented with severe asthma. 'We have not understood the correlation in India because we don't have that many cases presented to our clinic so far,' he says.
Asthma cannot be directly linked to night shifts, he explains, as there may be other reasons -- pollen allergies, colds and humidity -- with some individuals having more episodes in summer, while some others have increased episodes in winter. Besides, the standard guidelines for asthma have not listed night shifts as a risk factor as yet, he points out.
'We need to wait for larger studies from India in order to establish such a link. We need in-depth, robust randomised studies to find a direct correlation. A similar, large-scale study in India would help to understand the correlation between asthma and night shifts,' he says.
According to the WHO, asthma cannot be cured but there are several treatments available. The most common treatment is to use an inhaler, which delivers medication directly to the lungs. Inhalers can help control the disease and enable people with asthma to enjoy a normal, active life, it says.