Melatonin and sleep

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By Dr Simon Kyle

The use of melatonin as a sleep aid continues to be the subject of research studies worldwide. Findings thus far indicate that melatonin may be helpful for those suffering from disruptions to their circadian rhythm, or ‘body clock’.

What is naturally produced melatonin?
Melatonin, a hormone produced in the brain’s pineal gland, is responsible for the regulation of the body clock in each individual. Interestingly, the release of this hormone is largely controlled by exposure to natural light, or a lack thereof.

Melatonin production is first triggered in the evening, but the hormone continues to be released throughout the hours of darkness that follow (the conventional sleeping period). Levels of melatonin then drop with the breaking daylight and its production is suppressed until the next evening. Due to its dependence on a person being in a dark environment, melatonin is often referred to as the “hormone of darkness”.

It is precisely this link between darkness and melatonin, which informs advice to keep your bedroom dark and free from light-emitting electronics. Research has shown, for example, that both melatonin production and deep sleep phases are better maintained in the dark.

Melatonin and electric lighting
The introduction of electric light in the 19th century is often described as having had a negative influence on sleep. Before we had light bulbs and lamps in our homes, our circadian rhythms were dictated by natural light. People would wake with the first light of day and retire to bed early in the evening as the darkness fell.

The invention of artificial light however allowed people to make use of the evening after the sun went down. This change to our daily schedules is thought to have brought about changes in our sleep schedule, pushing our bedtime ever later.

Electric lighting continues to impact our sleep, not least because we are now free to work late into the evening and even throughout the night.

Melatonin sleep aids
Some research has suggested that melatonin supplements taken ahead of bedtime can help speed up the process of falling asleep and even improve sleep quality. There are limitations to this research however, having been conducted over a short time period. Thus far, this has prevented reliable conclusions being drawn about melatonin as a long-term solution for persistent poor sleep.

Additionally, sleep is influenced by other factors apart from melatonin production and, as with many other prescription and over-the-counter sleep aids, the benefits of melatonin supplements do not persist once people stop taking them. In the UK and parts of Europe, melatonin is licensed for those over the age of 55 with chronic insomnia, for whom it has shown evidence of sleep improvement.

Melatonin supplements are also commonly used as a “quick fix” by those who travel in an attempt to lessen the effects of jet lag. Further research is needed to establish whether melatonin supplements work any better than a placebo to minimize jet lag (Herxheimer and Petrie, 2002).

Do melatonin sleep aids have side effects?
Melatonin supplements are a relatively recent addition to the sleep aids market, having only gained popularity over the past decade or so. Research has therefore, only just begun to scratch the surface of the potential effects of melatonin, both negative and positive. It remains a future challenge therefore to answer questions such as when to take melatonin for sleep, or which melatonin dosage is best.

Melatonin is often seen as a ‘natural’ product when compared to prescription sleeping pills but this does not mean it escapes associated side-effects. So far, side-reported effects of melatonin include dizziness and headaches but long-term use of melatonin sleep aids has yet to be investigated.

Melatonin in older adults
Problems with sleep onset and maintenance in older adults are sometimes attributed to an age-related decrease in melatonin production. However, the results of research carried out to date has been mixed, meaning that further research is needed to establish whether age and melatonin production are indeed inversely proportional.

Herxheimer, A., Petrie, K.J. (2002). Melatonin for the prevention and treatment of jet lag. Cochrane Database System Review, (2): CD001520.

Filed under: Sleep aids