Melatonin may have an effect on nighttime blood pressure

The hormone melatonin -- known to influence sleep -- also may lower blood pressure.

In a study led by Dr. Frank A.J.L. Scheer, a neurologist at Harvard Medical School, 16 men with untreated hypertension were given 2.5 milligrams of melatonin before bedtime for three weeks. For another three weeks, they received a single dose of melatonin on the first night and placebos the other nights. Their blood pressure was monitored around the clock.

In the Jan. 20 online issue of Circulation: Journal of the American Heart Assn., the researchers reported that when the men took melatonin every evening, they had lower nighttime blood pressure readings than when they took only a single dose of melatonin. Nightly melatonin use reduced blood pressure by an average of 6 points for the upper (systolic) reading and 4 points for the lower (diastolic) reading.

Doctors worry about elevations in nighttime blood pressure because they are a stronger predictor of cardiovascular risk than daytime readings.

The study’s authors say taking melatonin at night could be an alternative or supplement to regular hypertension drugs.

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Jane E. Allen