Researchers found that the circadian system contributes to the common nighttime worsening of asthma, according to data published in Proceedings of the National Academy of Sciences of the United States of America.

“For centuries, it has been recognized that asthma severity shows a daily rhythm, with the worst symptoms at night,” Frank A.J.L. Scheer, MSc, PhD, of the division of sleep medicine at Harvard Medical School, and colleagues wrote. “However, it is unclear to what degree this is driven by everyday behaviors, such as sleep, physical activity and body posture changes, versus intrinsic rhythms generated by the internal body clock.”

Scheer and colleagues wrote that the body’s circadian system may influence the pulmonary and inflammatory system via the automatic nervous system, humoral factors and local molecular clocks.

To determine the independent effect of the endogenous circadian system on asthma, the researchers enrolled patients with asthma without steroid use and a group of control participants in two complementary in-laboratory protocols.

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