Study explores why asthma worsens at night

As many as 75 percent of people with asthma — 20 million people in the U.S. — report experiencing worsening asthma severity at night. Many behavioral and environmental factors, including exercise, air temperature, posture, and sleep environment, are known to influence asthma severity. Scheer, Shea, and colleagues wanted to understand the contributions of the internal circadian system to this problem. The circadian system is composed of a central pacemaker in the brain (the suprachiasmatic nucleus) and "clocks" throughout the body and is critical for the coordination of bodily functions and to anticipate the daily cycling environmental and behavioral demands.

To disentangle the influence of the circadian system from that of sleep and other behavioral and environmental factors, the researchers enrolled 17 participants with asthma (who were not talking steroid medication, but who did use bronchodilator inhalers whenever they felt asthma symptoms were worsening) into two complementary laboratory protocols where lung function, asthma symptoms and bronchodilator use were continuously assessed. In the "constant routine" protocol, participants spent 38 hours continuously awake, in a constant posture, and under dim light conditions, with identical snacks every two hours. In the "forced desynchrony" protocol, participants were placed on a recurring 28-hour sleep/wake cycle for a week under dim light conditions, with all behaviors scheduled evenly across the cycle.

Reference:

The study titled, "The endogenous circadian system worsens bronchial asthma at night time impartial of sleep and different every day behavioral or environmental cycles," is published in the Proceedings of the National Academy of Sciences.

DOI: 10.1073/pnas.2018486118