Melatonin may have a future role in treatment of essential hypertension through regulation of circadian rhythm, according to an article in the January 20th rapid access issue of Circulation.

“It has been reported that people with high blood pressure often have suppressed nighttime melatonin levels,” said Frank Scheer, PhD, the lead author of the study. “We have recently found that people with high blood pressure have actual anatomical disturbances of their biological clocks. This finding might open the door for a new approach for treating hypertension.”

In the current study, researchers at a Dutch institute evaluated melatonin’s effect after a single dose and after repeated nightly doses. For 3 weeks, researchers gave 16 men with untreated essential hypertension either 2.5 mg oral melatonin on 1 night and placebo on the others or 2.5 mg oral melatonin every night 1 hour before bedtime.

The overnight systolic blood pressure of patients on nightly melatonin decreased by 6 mm Hg, while diastolic pressure decreased by 4 mm Hg. The single dose of melatonin had no effect on blood pressure. Patients who received nightly melatonin also reported improved sleep, but Scheer said that the effect was unrelated to blood pressure reduction.

Although this small study suggests regulation of circadian rhythms might be a mechanism involved in blood pressure reduction, the authors do not exclude the possibility that improved sleep over a long time might help reduce blood pressure as well.

Dan Jones, MD, an American Heart Association spokesperson and hypertension expert, added a word of caution about the study findings: “This report showing a blood pressure-lowering effect of melatonin use is of interest primarily at a theoretical or research level. Larger studies certainly would be needed prior to recommending this approach to patients with high blood pressure.”

Scheer agreed. “This is just a start. Large-scale studies need to be done, as well as studies of potential interactions between melatonin and traditional antihypertensive treatments.”