Melatonin and Myocardial Infarction: What is the Association?

The professional literature is replete with news of melatonin’s interaction with the cardiovascular system. Patients with low nocturnal melatonin secretion are more likely to have cardiovascular risk factors, diabetes, and hypertension, and patients with active cardiovascular disease commonly have lower nocturnal melatonin levels.

Researchers from Brigham and Women’s Hospital and Harvard University in Boston, MA, set out to determine if melatonin secretion predicts myocardial infarction (MI). Their findings, published in the British Medical Journal, indicate lower melatonin secretion translated to increased risk of incident MI in women with increased body mass index (BMI).

This prospective nested case—control study examined women enrolled in the Nurses’ Health Study cohorts 1 and 2. The researchers were able to identify 209 incident cases of fatal and non-fatal MI. They matched this group to 209 controls.

The researchers measured nocturnal melatonin secretion using 6-sulfatoxymelatonin concentrations in morning urines.

Women with the lowest melatonin secretion were 1.51 times more likely to have an MI than those who had highest levels. In addition, when the researchers controlled for factors included in the American Heart Association Cardiovascular Risk Score plus circadian factors, they found that a drop of just 1 unit in a woman’s urine 6-sulfatoxymelatonin/creatinine ratio increased risk of MI by about 1.4 times.

Women in the highest category had an estimated absolute risk of MI of 84 cases per 100,000 person-years. Women in the lowest group experienced 197 MIs per 100,000 person-years. BMI also correlated with increased risk of MI.

The researchers conclude that melatonin may be a modifiable risk factor for MI among women, and represents a potentially new intervention. Randomized control trials should investigate its effect on established cardiovascular risk factors.