Meta-Analysis: Melatonin for the Treatment of Primary Sleep Disorders
This Research brief is summarized from a published clinical study. All the information and statistics cited below were taken directly from the original publication piloted by Ferracioli-Oda, et al.1 NutraScience Labs has restructured or paraphrased some sections of this brief in an attempt to more succinctly summarize the research.
In order to be diagnosed with a primary sleep disorder, the sleep disturbance must cause significant distress or impairment in social, occupational, or other areas of functioning. Primary sleep disorders are not associated with a medical condition, substance use or concurrent psychological disorder. Poor sleep is also associated with an increased risk of mortality, hospitalization and traffic accidents.Statistics show that 9% of Americans report having insomnia. There are numerous therapies for the treatment of insomnia ranging from psychological or behavioural therapies to medications.
Many trials have been performed to assess the efficacy of exogenous melatonin in treating primary sleep disorders. Melatonin is a hormone secreted by the pineal gland in response to variations in the circadian cycle. It has been used for the last two decades for the treatment of sleep disorders. Melatonin has little potential for dependency and has been widely utilized in the United States.
This study seeks to examine melatonin’s effects on sleep latency, total sleep time and sleep quality.It will also examine the moderating effects of measure type, dose and duration of melatonin treatment.
Selection of Studies
PubMed was searched by two reviewers using the terms Melatonin and Sleep Disorder. The search was further limited to include only randomized controlled trials and meta-analyses. All studies included were published before or on March 2012.
Trials were only included if they analyzed primary sleep disorders as defined by the DSM-IV, examined the effects of melatonin, were randomized placebo controlled trials, had at least 10 participants for parallel designs or 5 participants for crossover designs and were published in English.
Data was extracted using Microsoft Excel spreadsheets.The primary outcome measure was mean improvement in sleep onset latency, total sleep time and sleep quality.The difference between melatonin and placebo was examined by calculating the weighted mean difference (WMD). A fixed-effects model was used for this meta-analysis with the results for a random-effects model presented as a sensitivity analysis.
For secondary analyses, several subgroup analyses and meta-regressions were performed. Stratified subgroup analysis was used to assess the effects of type of measure (subjective/objective). Meta-regression was performed to examine the association between melatonin efficacy in trials and continuous variables such as dose and duration.All data including information on the inclusion/exclusion of studies and extraction of data for meta-analysis is available from the corresponding author by request.
Nineteen studies involving a total of 1683 subjects were included in this meta-analysis. From the search on PubMed and related bibliography 268 studies were selected.
Sleep Onset Latency
The meta-analysis showed that melatonin had a large contribution to reducing sleep latency. Subjects randomly assigned to melatonin fell asleep 7 minutes earlier on average than subjects receiving the placebo.
Total Sleep Time
Melatonin also significantly increased total sleep time compared to placebo. Subjects randomly assigned to melatonin had on average a total sleep time 8 minutes longer than subjects taking placebo.
Melatonin showed large improvements in sleep quality as well. Subjects randomly assigned to melatonin had improvements in sleep quality compared to placebo.
DISCUSSION AND CONCLUSION
The meta-analysis demonstrated that melatonin improved sleep in subjects with primary sleep disorders compared to subjects who took the placebo. Melatonin also reduced sleep-onset latency, increased the total sleep time and improved overall sleep quality compared to subjects in the placebo group to a statistically significant degree.
Meta-regressions were performed to assess the relationship between effect, duration and dose. Higher melatonin doses and longer duration trials were related to significant greater effect sizes on sleep latency and total sleep time. These findings suggest that there is no evidence of the development of tolerance with melatonin use.
No greater effects in sleep quality were observed with melatonin dose or trial duration.This showed that melatonin effects on sleep quality are constant regardless of duration or dose.
Because of the relatively small number of trials that were included, the meta-regression analysis had a limited range. The small number of trials also limited the ability of the Egger’s Test to demonstrate publication bias. However there was no evidence of publication bias for all outcome measures on funnel plot as well.
In spite of these limitations, the meta-analysis showed that exogenous melatonin administered to subjects with primary sleep disorders modestly improved sleep parameters including sleep latency, total sleep time and sleep quality. Further research is needed to examine the long-term benefits of sleep medications including the comparative efficacy of melatonin to common prescription sleep medication.
1. Ferracioli-Oda E, Qawasmi A, Bloch MH (2013) Meta-Analysis: Melatonin for the Treatment of Primary Sleep Disorders. PLoS ONE 8(5): e63773. doi:10.1371/journal.pone.0063773