Medical experts and patients have been seeking an answer for this asthmatic question since hundreds of years. Why does the severity of Asthma worsen at night time? Experts have come up with several analysis, possibilities and ailments, but none of them had proven completely right or useful. More than 75 per cent of people with asthmatic conditions report experiencing worsening severity of asthma at night. Many behavioural and environmental factors, including exercise, posture, air temperature and sleep environment, are proved to influence asthma severity.
A recent study conducted by the team from Brigham and Women’s Hospital and Oregon Health and Science University, have successfully analysed the contributions of the internal circadian system to this problem. Using two circadian protocols, investigators from the University have pinned down the influence of the circadian system, uncovering a key role for the biological clock in asthma.
The circadian system composes a central pacemaker in the brain, (the suprachiasmatic nucleus) and ‘clocks’ throughout the body. It is essential for the coordination of bodily functions, and to anticipate the daily cycling behavioural and environmental demands.
To extricate the influence of the circadian system, from other behavioural and environmental factors and sleep, the researchers involved 17 participants with asthma for the study. The enrolled participants were not taking steroid medication, but did use bronchodilator inhalers whenever they felt asthma symptoms were worsening. They were admitted into two complementary laboratory protocols where lung function, asthma symptoms and bronchodilator use were continuously measured. In the “constant routine” protocol, participants were made to spent 38 hours being continuously awake, in a constant posture, and under dim light conditions, with identical snacks every two hours. In this “forced desynchrony” protocol, participants were placed on a recurring 28-hour sleep/wake cycle for a week under dim light conditions, with all behaviours organized evenly throughout the cycle.
‘We observed that those people who have the worst asthma in general are the ones who suffer from the greatest circadian-induced drops in pulmonary function at night, and also had the greatest changes induced by behaviours, including sleep’, Steven A. Shea, Professor and director at Oregon Institute of Occupational Health Sciences, explained the results of the study. ‘This is one of the first studies to carefully isolate the influence of the circadian system from the other factors that are behavioural and environmental, including sleep’, points out Frank AJL Scheer, director of the Medical Chronobiology Programme in the Division of Sleep and Circadian Disorders at the Brigham.
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