The hormone melatonin may be a factor in the worsening of nocturnal asthma, according to a study published in the September Journal of Allergy and Clinical Immunology (JACI). The JACI is the peer-reviewed journal of the American Academy of Allergy, Asthma and Immunology (AAAAI).

Melatonin, a hormone produced by the pineal gland, is an important regulator of the body's circadian rhythms, such as eating or sleeping. The hormone is also widely available as an over-the-counter medication, used by millions of Americans to treat jet lag and insomnia. However, recent studies have shown that melatonin enhances allergic airway inflammation and may have adverse effects on asthma symptoms.

A research team led by E. Rand Sutherland from National Jewish Medical and Research Center in Denver investigated the relationship between melatonin and severity of nocturnal asthma by evaluating 24-hour melatonin levels in a test group consisting of healthy patients, nocturnal asthmatics and non-nocturnal asthmatics.

Researchers found that patients with nocturnal asthma have melatonin levels that are significantly higher than healthy subjects. The study also found that higher melatonin levels are associated with more severe nocturnal worsening of asthma.

Asthma is a chronic inflammatory disease of the lungs that affects more than 20 million Americans. Nearly 75% of patients with asthma experience increased symptoms at night. Nocturnal asthma, also referred to as sleep-related asthma, is characterized by increased airway inflammation during the hours of sleep, with symptoms the worst between midnight and 4 a.m.

Researchers estimate that 6% of asthma sufferers use melatonin as a sleep aid. Since melatonin enhances inflammation and that higher levels are associated with more severe nocturnal asthma symptoms, it is suggested that people with asthma should avoid taking over the counter medications until further research explains the clinical effect.