<aside> 💡 Experiment Results Summary:
**Weighted blankets don't appear to robustly improve sleep quality or efficacy.
Thus, no blanket recommendations should be made for weighted blankets.** 😏
</aside>
About a year ago, a housemate and my girlfriend (at the time) both got weighted blankets and suggested they obtained benefits from it - they found that the blankets helped them sleep better, reduce anxiety, and generally felt comfortable.
These claims piqued my curiosity and I looked into weighted blankets.
I didn't find much research (as I've outlined elsewhere.) Regardless of this dearth of evidence and the often non-trivial cost associated, they've become very trendy and are frequently justified with quasi-therapeutic claims.
This seemed like an investigation that's very tractable to my self-experimentation methods, especially coupled with the fact that I'm not coupled (i.e., I'm (now) single & sleep alone 😅 and therefore have far fewer potential sleep confounds.)
So, for 100 nights, I set up a random assignment of sleeping with a weighted blanket for 50 nights and 50 nights without. I skipped nights where there was any meaningful confound I could anticipate, e.g., if I was drinking or staying up late. In principle, any other minor confounds would wash out in the data given we wouldn't expect any systematic bias in them.
I would measure various biometrics with my Oura ring as well as take a subjective evaluation of my sleep every morning. At the end of the experiment, I would analyze the results to see any differences.
And what did I find?
Essentially nothing.
With the exception of REM duration, there's no meaningful or statistically significant difference in either objective or subjective sleep outcomes between the nights when I slept with a weighted blanket and when I slept without one.
I've included the data tables and graphs below.
For subjective sleep quality, Oura readiness score, Oura sleep score, heart rate, heart rate variability, sleep efficiency, the scores were very tightly aligned without any statistically significant difference.
However, with deep sleep and REM sleep duration, there's a some more interesting data elements.
Sleeping with a weighted blanket seems to decrease deep sleep by around 6 minutes (p = 0.06) but increases REM sleep by the same amount (p = 0.03.)