If you have asthma, you may well find that stress makes your symptoms worse. But a new study shows that stress may actually be a cause of asthma too. The effect is only small - but it's significant, because it might help us understand more about how asthma works.
Writing in the Allergy journal, Dr. Adrian Loerbroks and his team at Heidelberg University in Germany, described a study of over 5,000 adults followed up for nearly ten years. Those who reported high job stress at the start were twice as likely as those with low levels of job stress to develop asthma. However, the absolute numbers of new asthma cases were low. The study found that 2.4% of those reporting a lot of stress at work developed asthma, compared to 1.2% of those who were not stressed. Also, this study does not actually prove that occupational stress causes asthma - it just demonstrates a link. It could be that there is some underlying common factor that makes people feel stressed and also predisposes them to asthma.
The researchers note that there is other evidence that chronic stress exposure, distressing life events, and stress-related personality traits also increase the risk of asthma. But this is the first study to show a link between work-related stress and new cases of asthma. We already know that job stress, particularly lack of control over workload, can cause increased risk of heart disease, diabetes and depression - probably also through chronic exposure of the body to the stress hormone cortisol. It may be that some similar effect is operating among people susceptible to asthma experiencing job stress.
It's easy to say you feel stressed by work, but how do researchers measure it? In this study, the participants were asked how much strain they felt at work and how often, at the end of the working day, they were still thinking about their job or felt exhausted or unable to cope. Not only did those with high work stress have a greater risk of developing new asthma, but those reporting stress were also more likely to have asthma to start with.
So the link between stress and asthma is quite complex. It may be that chronic stress has an impact upon the hormonal and immune systems which goes on to affect the airways. Further investigation of the link by research would probably be worthwhile. But reducing occupational stress would only prevent a very few cases of asthma, as the numbers involved in this study are so small. Companies should, instead, focus upon keeping employees safe at work by reducing exposure to triggers and indoor pollution. This study reflects recent findings on outdoor pollution and asthma. It used to be thought that pollutants like particulate matter merely worsened existing asthma. Now a report from the Committee on the Health Effects of Air Pollution showed that air pollution, particularly near busy roads, can actually cause asthma in people with a genetic susceptibility to the disease.
Loerbroks A et al Work-related stress, inability to relax after work and risk of adult asthma: a population-based cohort study Allergy 2010;65:1298-305