A weighted blanket of approximately 12% body weight used at bedtime prompted the release of higher concentrations of melatonin, as measured in the saliva, compared with a lighter blanket of only about 2.4% of body weight.
This suggests that weighted blankets may help promote sleep in patients suffering from insomnia, according to the results from the small, in-laboratory crossover study.
"Melatonin is produced by the pineal gland and plays an essential role in sleep timing," lead author Elisa Meth, PhD student, Uppsala University, Sweden, and colleagues observe.
"Using a weighted blanket increased melatonin concentration in saliva by about 30%," Meth added in a statement.
"Future studies should investigate whether the stimulatory effect on melatonin secretion remains when using a weighted blanket over more extended periods," the researchers observe, and caution that "it is also unclear whether the observed increase in melatonin is therapeutically relevant."
The study was published online October 3 in the Journal of Sleep Research.
Weighted blankets are commercially available at least in some countries in Scandinavia and Germany, as examples, and in general, they are sold for therapeutic purposes. And at least one study found that weighted blankets were an effective and safe intervention for insomnia in patients with major depressive disorder, bipolar disorder, generalized anxiety disorder, and attention deficit hyperactivity disorder (ADHD) and led to improvements in daytime symptoms and levels of activity.
Study Done in Healthy Volunteers
The study involved a total of 26 healthy volunteers, 15 men and 11 women, none of whom had any sleep issues. "The day before the first testing session, the participants visited the laboratory for an adaptation night," the authors observe. There were two experimental test nights, one in which the weighted blanket was used and the second during which the lighter blanket was used.
On the test nights, lights were dimmed between 9 PM and 11 PM and participants used a weighted blanket covering the extremities, abdomen, and chest 1 hour before and during 8 hours of sleep. As the authors explain, the filling of the weighted blanket consisted of honed glass pearls, combined with polyester wadding, which corresponded to 12.2% of participants' body weight.
"Saliva was collected every 20 minutes between 22:00 and 23:00," Meth and colleagues note. Participants' subjective sleepiness was also assessed every 20 minutes using the Karolinska Sleepiness Scale both before the hour that lights were turned off and the next morning.
"Sleep duration in each experimental night was recorded with the OURA ring," investigators explain.
The OURA ring is a commercial multisensor wearable device that measures physiological variables indicative of sleep. Investigators focused on total sleep duration as the primary outcome measure.
On average, salivary melatonin concentrations rose by about 5.8 pg/mL between 10 PM and 11 PM (P < .001), but the average increase in salivary melatonin concentrations was greater under weighted blanket conditions at 6.6 pg/mL compared with 5.0 pg/mL during the lighter blanket session (P = .011).
Oxytocin in turn rose by about 315 pg/mL initially, but this rise was only transient, and over time, no significant difference in oxytocin levels was observed between the two blanket conditions. There were also no differences in cortisol levels or the activity of the sympathetic nervous system between the weighted and light blanket sessions.
Importantly, as well, no significant differences were seen in the level of sleepiness between participants when either blanket was used nor was there a significant difference in total sleep duration.
"Our study cannot identify the underlying mechanism for the observed stimulatory effects of the weighted blanket on melatonin," the investigators caution.
However, one explanation could be that the pressure exerted by the weighted blanket activates cutaneous sensory afferent nerves, carrying information to the brain. The region where the sensory information is delivered stimulates oxytocinergic neurons that can promote calm and well-being and decrease fear, stress, and pain. In addition, these neurons also connect to the pineal gland to influence the release of melatonin, the authors explain.
Melatonin Often Viewed in the Wrong Context
Senior author Christian Benedict, PhD, associate professor of pharmacology, Uppsala University, Sweden, explained that some people think of melatonin in the wrong context.
In point of fact, "it's not a sleep-promoting hormone. It prepares your body and brain for the biological night...[and] sleep coincides with the biological night, but it's not like you take melatonin and you have a very nice uninterrupted slumber — this is not true," he told Medscape Medical News.
He also noted that certain groups respond to melatonin better than others. For example, children with attention deficit hyperactivity disorder (ADHD) may have some benefit from melatonin supplements, as may the elderly who can no longer produce sufficient amounts of melatonin and for whom supplements may help promote the timing of sleep.
However, the bottom line is that, even in those who do respond to melatonin supplements, they likely do so through a placebo effect that meta-analyses have shown plays a powerful role in promoting sleep.
Benedict also stressed that just because the body makes melatonin, itself, does not mean that melatonin supplements are necessarily "safe."
"We know melatonin has some impact on puberty — it may delay the onset of puberty — and we know that it can also impair blood glucose, so when people are eating and have a lot of melatonin on board, the melatonin will tell the pancreas to turn off insulin production, which can give rise to hyperglycemia," he said.
However, Benedict cautioned that weighted blankets don't come cheap. A quick Google search brings up examples that cost upwards of $350. "MDs can say try one if you can afford these blankets, but perhaps people can use several less costly blankets," he said. "But I definitely think if there are cheap options, why not?" he concluded.
Benedict has reported no relevant financial relationships.
J Sleep Res. Published online October, 3, 2022. Full text
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Cite this: Weighted Blankets Promote Melatonin Release, May Improve Sleep - Medscape - Oct 07, 2022.