Taking a pill containing melatonin, a natural hormone that regulates sleep, at bedtime may enhance the drop in blood pressure that occurs at night, Italian investigators report, thereby protecting the heart from damage.

The normal decline in blood pressure at night is related to the rise of melatonin levels in the body, Dr. Angelo Cagnacci, from Policlinico di Modena, and colleagues note. Therefore, treatment with melatonin might be expected to lower blood pressure further.

To evaluate the effect of melatonin on blood pressure changes in women, Cagnacci’s group recruited nine healthy women and nine women who were being successfully treated with drug therapy for high blood pressure.

For three weeks, the women were randomly assigned to pills containing melatonin or inactive “placebo.” After the three weeks, the women crossed over to the alternate treatment.

According to the report in the American Journal of Hypertension, melatonin treatment decreased nighttime blood pressure. As a result, the day-night blood pressure difference was more pronounced during melatonin use. The drug had no effect on daytime blood pressure or on heart rate.

Because a low day-night ratio for blood pressure has been linked to heart disease, Cagnacci and his team note, increasing the day-night ratio by melatonin treatment may have a protective effect on the heart.

SOURCE: American Journal of Hypertension, December 2005.