A new evidence review by the University of Alberta Evidence-based Practice Center (EPC), which is supported by the Agency for Healthcare Research and Quality (290-02-0023), focuses on the use of melatonin supplements for the treatment of a variety of sleep disorders. According to the EPC researchers who conducted the review, melatonin supplements appear to be safe when used over a period of days or weeks at relatively high doses and in various formulations. However, the safety of melatonin supplements used over months or even years is unclear.
Although there is some evidence for the benefits of melatonin supplements, for most sleep disorders the authors found evidence suggesting limited or no benefits. But, according to the authors, firm conclusions cannot be drawn until more research is conducted. The report was requested and funded by the National Center for Complementary and Alternative Medicine, a component of the National Institutes of Health.
The researchers reviewed the scientific evidence to date for the benefits of melatonin supplements used for disorders due to sleep schedule alterations and primary and secondary sleep disorders. Disorders due to sleep schedule alterations can stem from flying across time zones or working night shifts. Primary sleep disorders, which include insomnia, can be caused by factors such as stress or drinking too much caffeinated coffee. Secondary sleep disorders also may include insomnia, but patients in this category also have underlying mental disorders, such as psychoses or mood and anxiety disorders, neurological conditions such as dementia or Parkinson's disease, or chronic pulmonary disease.
In its natural form, melatonin is produced by the brain's pineal gland to regulate the sleep cycle. In the evening, the level of the hormone in the bloodstream rises sharply, reducing alertness and inviting sleep; in the morning, it falls back, encouraging wakefulness.
Among those problems for which melatonin supplements appear to provide little benefit are jet lag—a problem that often affects coast-to-coast travelers and those who fly through other time zones—as well as sleep problems that affect people who work night shifts.
In contrast, the authors found evidence to suggest that melatonin supplements may be effective when used in the short term to treat delayed sleep phase syndrome in people who have primary sleep disorders. In delayed sleep phase syndrome, a person's internal biological clock becomes "out of sync," making it difficult for the person to fall asleep until very late at night or to wake up early the next morning. But melatonin supplements may decrease sleep onset latency—that is, the time it takes to fall asleep after going to bed—in people with primary sleep disorders such as insomnia, although the magnitude of the effect appears to be limited.
Melatonin supplements do not appear to have an effect on sleep efficiency in people who have primary sleep disorders, and the effects of the hormone do not seem to vary by the individual's age, type of primary sleep disorder, dose taken, or length of treatment. Sleep efficiency refers to the percent of time a person is asleep after going to bed. Furthermore, melatonin supplements do not appear to affect sleep quality, wakefulness after sleep onset, total sleep time, or percent of time spent in rapid eye movement (REM) sleep. This most important phase of sleep is characterized by extensive physiological changes, such as accelerated breathing, increased brain activity, REM, and muscle relaxation.
In people with secondary sleep disorders, melatonin supplements do not appear to have an impact on sleep latency in either adults or children, regardless of dose or duration of treatment. On the other hand, the hormone does appear to modestly increase sleep efficiency, but it is not enough to be considered clinically significant. Melatonin supplements were not found to have an effect on wakefulness after sleep onset or the percent of time spent in REM sleep, but they do appear to increase total sleep time.
Estimates show that at least 40 million Americans each year suffer from chronic sleep disorders, and an additional 20 million people experience occasional sleep problems. Insomnia, the most common sleep disorder, affects 6 percent to 12 percent of adults, while 15 percent to 25 percent of children have difficulty initiating or maintaining sleep.
Sleep disorders cost an estimated $16 billion in medical costs alone each year. Indirect costs due to lost or substandard work productivity, accidents, resulting litigation, and other factors may increase total costs many times over. The National Highway Traffic Safety Administration, for example, estimates that 100,000 motor vehicle accidents a year are caused by driver fatigue from sleep deprivation—which is one result of some sleep disorders—and that more than 1,500 people are killed and another 71,000 injured annually as a result.
Copies of Melatonin for Treatment of Sleep Disorders, Evidence Report/Technology Assessment No. 108 (AHRQ Publication Nos. 05-E002-1, summary; 05-E002-2, full report) are available from the AHRQ Publications Clearinghouse.
In addition to the melatonin report, AHRQ has several other newly published evidence reports that were developed by AHRQ-supported EPCs. There are 13 AHRQ-supported EPCs. They systematically review the relevant scientific literature on topics assigned to them by AHRQ and conduct additional analyses when appropriate prior to developing their reports and assessments.
The goal is to inform health plans, providers, purchasers, and the health care system as a whole by providing essential information to improve health care quality. All of AHRQ's EPC reports, as well as several technical reviews, that have been published to date are available online and through the AHRQ Publications Clearinghouse.