, 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%,” Ms. 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 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 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,” Ms. 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.