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In a small study published in the October issue of the journal Sleep, people being treated for high blood pressure, or hypertension, who also took melatonin slept longer, fell asleep sooner and had more restful sleep than people taking an inactive placebo.
"The sleep community is well aware of the difficulties that beta blockers can cause with insomnia and sleep fragmentation," said Dr. Michael Yurcheshen, a physician with the Strong Sleep Disorders Center at the University of Rochester Medical Center in New York. "Although the sample size [in this study] is small, the results are compelling. If real-world experience parallels [these] lab results, such changes could make a significant clinical impact for these patients."
Yurcheshen, who is also an associate professor of neurology, was not involved with the study.
Not only are beta blockers widely prescribed to combat hypertension, they are also used for many other cardiovascular disorders as well as migraine, anxiety disorders and post-traumatic stress disorder.
Some 22 million people in the United States alone take a beta blocker regularly, according to background information in the study, with a common side effect being insomnia.
Beta blockers may affect sleep by inhibiting the release of melatonin, a hormone involved in regulating both sleep and the body's circadian clock.
To test the theory that melatonin supplementation might help people on beta blockers sleep better, researchers randomly assigned 16 adults with hypertension taking one of the beta blockers metoprolol or atenolol to also take either 2.5 milligrams of melatonin or a placebo every night for three weeks.
All of the patients underwent polysomnography, an overnight sleep test that records brain waves, muscle tone, heart rate and eye movements.
Participants who took melatonin slept an average of 36 minutes longer per night than those taking the placebo.
The treated participants also fell asleep 14 minutes faster, spent more time asleep while they were in bed (a measure known as "sleep efficiency") and spent an average of 41 minutes longer in stage 2 sleep, which is the longest sleep stage, usually taking up more than 50 percent of a person's sleep time.
"Melatonin reduced their time awake from about 20 percent to just 12 percent, almost halving their wake time during the night," said Frank Scheer, lead study author and director of the medical chronobiology program at Brigham and Women's Hospital in Boston.
Participants didn't report any differences in mood or energy levels but such subjective measures vary more than objective measures such as those recorded by polysomnography, Scheer said.
And melatonin levels in the body did rise.
"We showed a very clear increase with supplementation of melatonin at night," said Scheer, who is also an assistant professor of medicine at Harvard Medical School.
Melatonin has several advantages over many drugs prescribed to aid sleep.
People on melatonin didn't have a "rebound" effect of seeing their sleep deteriorate after going off the supplements, as happens with many sleep drugs.
In addition, said Scheer, "we found a carry-over effect of a benefit, so even when participants stopped taking melatonin, there was still some benefit."
Nor was there any sign of increased tolerance leading to a need for higher doses of the drug. "Indeed, melatonin remained effective across each of the three weeks of supplementation," Scheer said.
"There are some apparent benefits of melatonin as opposed to other hypnotics," said Scheer, who nevertheless pointed out that the study is a small one and needs to be confirmed in larger trials.
Melatonin is widely available as an over-the-counter supplement and studies have shown it to be relatively safe for up to half a year, Scheer said. There are no studies that document its safety beyond that time point.
Anyone considering taking melatonin should speak with their doctor or health care provider, Scheer said.
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