Sleep Research Library

Temperature is king. Across 4 RCTs and observational studies, sleeping in a 65-68°F (18-20°C) environment improved total sleep time by 15-25 minutes and increased deep sleep by 10-20%. Active cooling mattresses (Eight Sleep, ChiliPad) showed the strongest effect.

Medium-firm wins for pain. The Lancet meta-analysis (Kovacs et al.) and 3 follow-up studies converge: medium-firm mattresses reduce chronic low-back pain more effectively than firm beds. Innerspring-over-foam hybrids performed best.

Light exposure matters more than supplements. Blue light after 9pm suppresses melatonin by up to 50% and delays circadian phase by 30+ minutes. Blocking evening blue light is more effective than taking exogenous melatonin for most adults without diagnosed circadian disorders.

Weighted blankets help anxiety-related insomnia. The Karolinska RCT (Ekholm et al., 2020) showed weighted blankets improved insomnia severity and reduced daytime drowsiness — but the benefit was strongest in patients with comorbid anxiety. Evidence for general-population use is weaker.

Consumer trackers are getting accurate. Oura Ring Gen 3 and Apple Watch show 85-90% agreement with PSG for total sleep time. Sleep stage detection is still unreliable across all consumer devices — don't optimize for "deep sleep" scores.