Sleep Disorders, Age related illnesses | June 3, 2015 | Author: The Super Pharmacist
Melatonin is a natural hormone made by the pineal gland, a neuroendocrine organ situated in the midline of the brain. It plays a central role in the coordination of circadian rhythms and a wide variety of daily bodily functions. A circadian rhythm is a coordinated physiological, psychological, and behavioural process that is genetically programmed to synchronise with night and day and, amongst other things, helps regulate the sleeping pattern.
Throughout the daytime, the pineal gland is inactive. In the evening, and in direct response to a lack of light, the pineal gland is activated by the suprachiasmatic nucleus (SCN) which acts like a regulatory clock within the body, providing us with a number of signals and actions such as the release of melatonin to prepare our body for sleep. Stimulation from the SCN results in high levels of melatonin in the blood in the late evening, preparing the body for sleep. Melatonin levels then remain high for approximately 12 hours, all the way through sleep, and begin to decrease significantly on waking up. Daytime levels of melatonin are barely detectable as part of the circadian rhythm, when sunlight (or artificial light in some circumstances) triggers a process in the SCN that suppresses the release of melatonin. Irregular disruptions to this process and the circadian rhythms can result in a number of health problems, including disrupted sleep and, in more severe cases, insomnia.
The medical definition of insomnia is ‘difficulty in getting to sleep, difficulty staying asleep, early wakening, or non-restorative sleep despite adequate time and opportunity to sleep. These disruptions result in impaired daytime functioning; such as poor concentration, mood disturbance, and daytime tiredness. It can be triggered by a number of factors, such as age and ageing, jet lag, shift work, exposure to bright light at night, or damage to the retino-hypothalmic tract or pineal gland (this is common in blind people with no light perception, who frequently display free-running circadian rhythms).
Yes, largely as a result of biological changes to the pineal gland. It is at its largest during puberty but continues to decrease in size and functionality with age, with studies consistently showing that older people have impaired melatonin production when compared with age-matched controls (1). There is also a clearly defined causal relationship between shift work and the clinical diagnosis of insomnia, with a recent study of shift working female nurses showing a higher incidence of insomnia compared to a standard-shift pattern population, and higher associated anxiety and depression. The same study, conducted by a group of research neuroscientists in the US, also found that a daytime darkness procedure, by which the nurses replicated the experience of night time to invoke their regular circadian rhythms, significantly improved their insomnia and resulted in more improved sleep and performance at work (2).
Generally, there is limited evidence regarding the efficacy of melatonin use in a wide variety of populations experiencing insomnia or other sleep disorders. There are a limited number of studies regarding the use of melatonin in the treatment of children under the age of 16 with sleep disorders, but there is very little available data regarding its effectiveness, with most research questions focusing on the relationship between melatonin use and its safety in regards to pubertal development (3).
A large number of tests comparing the use of melatonin to treat insomnia versus a placebo have found there to be no benefit of melatonin used in isolation as an effective treatment for insomnia (4). Evidence that melatonin can reset the body clock is more well established (5), and a number of further studies have indicated that melatonin, taking at the appropriate time, is effective for reducing insomnia associated with jetlag and shift work (6). Appropriate dosage issues and potential concerns around safety require further research.
The timing of melatonin use remains an important factor in its efficacy, with a range of studies showing that taking it early in the day is counterproductive and results in drowsiness and a lack of effective sleep at night (7). There are a number of smaller studies that suggest low doses of melatonin are effective in alleviating the symptoms of insomnia in selective samples of older insomniacs, although many of the studies included in the systematic review, conducted in 2001, were of such small samples that they were not always statistically significant (8).
Many of the studies did not take into account the wide range of confounding variables that could also impact on an older person’s experience of insomnia, and were prone to overestimating the effects of melatonin treatment. All patients who are considering taking melatonin are urged to do so carefully in countries where it is available in a number of different supplementary formats and without pharmaceutical prescription.
The production of synthetic melatonin is not regulated, and therefore dosage levels offered commercially can be significantly higher than those prescribed by medical professionals. As little is known regarding the relationship between dosage and safety, it is generally recommended that individuals considering taking melatonin supplements consult with their health professional first. Further large, randomised controlled trials are required to demonstrate if melatonin is effective and safe for insomnia, particularly for long-term use.
1. Hardeland R (2012) Melatonin in ageing and disease – multiple consequences of reduced secretion, options and limits of treatment Ageing Dis 3(2):194-225
2. Smith MR, Fogg LF, Eastman CI (2009) A compromise circadian phase position for permanent night work improves mood, fatigue, and performance Sleep 32(11):1481-9
3. van Geijlswijk IM, Mol RH, Egberts TC, et al (2011) Evaluation of sleep, puberty and mental health in children with long-term melatonin treatment for chronic idiopathic childhood sleep onset insomnia Psychopharmacology 216(1):111-20
4. Garzon C, Guerrerro JM, Aramburu O, Guzman T (2009) Effect of melatonin administration on sleep, behavioral disorders and hypnotic drug discontinuation in the elderly: a randomized, double-blind, placebo-controlled study Aging Clin Exp Res 21(1):38-42
5. Amirian I, Andersen LT, Rosenberg J, Gogenur I (2015) Working night shifts affects surgeons’ circadian rhythm Am J Surg doi: 10.1016/j.amjsurg.2014.09.035
6. Chalubinski M, Wojdan K, Broncel M et al (2014) The effect of melatonin on circadian blood pressure in patients with type 2 diabetes and essential hypertension Arch Med Sci 29:10(4):669-75
7. Weingarten JA, Collop NA (2013) Air travel: effects of sleep deprivation and jet lag Chest 144(4):1394-401
8. Olde Rikkert MG, Rigaud AS (2001) Melatonin in elderly patients: a systematic review Z Gerontol Geriatr 34(6):491-7