Sleep Hormone Melatonin May Worsen Asthma

For some asthma patients, symptoms such as chest tightness, shortness of breath, cough, and wheezing can get worse at night. This so-called "nocturnal asthma" can be a sign that asthma control is deteriorating. Previous research has shown that more than half of asthma-related deaths occur at night.

While the sleep hormone melatonin has been shown to improve sleep for some individuals with asthma (and possibly provide an anti-inflammatory effect), a research group led by Kentaro Mizuta, DDS, PhD, a professor at Tohoku University Graduate School of Dentistry in Japan, has discovered that melatonin could actually worsen asthma.

In data from lab testing published November 16 in the journal Lung Cellular and Molecular Physiology, Dr. Mizuta and his colleagues demonstrated that melatonin can exasperate the constriction of the bronchus, the pathway that moves air to and from your lungs. With bronchoconstriction, the smooth muscles of the bronchus contract, making it harder to breathe.

To relieve the constriction, people with asthma often use a bronchodilator, a medicine which widens the bronchus. Lab testing also revealed that melatonin also weakens the relaxing effect of a bronchodilator, a medicine which widens the bronchus.

“Previous research showed that melatonin might have some anti-inflammatory benefits and was a relatively safe supplement for patients,” said Payel Gupta, MD, a spokesperson for the American Lung Association, who was not involved in this study. “This research is important for patients as the use of over-the-counter supplements is rampant. It is important for consumers to know that some ‘natural’ remedies for sleep like melatonin can in fact pose a threat.”

Mizuta acknowledges that melatonin is often prescribed to people with insomnia, psychiatric disorders, cancers, or cardiovascular diseases not only because of its therapeutic effects but also due to it causing relatively few side effects.

“Our findings suggest, however, that pharmacological concentrations of melatonin [used to treat insomnia, jet lag, or cancer] would contribute to airway smooth-muscle contraction by the stimulation of melatonin MT2 receptor expressed on human airway smooth muscle, leading to bronchoconstriction, which could worsen asthma symptoms,” said Mizuta.

Jon Romeo, DO, chair of the American College of Allergy, Asthma, and Immunology Asthma Committee, credits the study for more clearly defining how the melatonin MT2 receptor plays a role in bronchoconstriction.

“Overall, I think this [research] supports the cautious use of exogenous melatonin [not produced by the body, but manufactured] in those with asthma, especially nocturnal asthma,” said Dr. Romeo. “It also suggests MT2 as a possible target for future therapy.”

Pharmacological therapy that blocks the melatonin MT2 receptor could inhibit the detrimental effects of melatonin on airways, added Haruka Sasaki, DDS, also with Tohoku University and first author of the paper.

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