Sleep on a high heat capacity mattress increases conductive body heat loss and slow wave sleep.
Level 2 - randomized trial
Randomized crossover trial in humans
PubMed 29247670 · doi:10.1016/j.physbeh.2017.12.014
What was done
In a randomized single-blind crossover study, 15 healthy young men (mean age 26.9 ± 2.1 years, BMI 22.2 ± 0.4 kg/m²) were evaluated during overnight sleep in a temperature-stabilized laboratory on a high heat capacity mattress (HHCM) versus a conventional low heat capacity mattress (LHCM). Researchers continuously recorded standard video-polysomnography, core body temperature (CBT), skin temperatures (including proximal back skin, PROBA), and mattress surface temperatures. Subjective sleep quality was measured using a visual analogue scale.
What was found
Compared to the LHCM, sleeping on the HHCM resulted in: - A 16% selective increase in slow wave sleep (SWS; p < 0.05), with increased SWS and reduced REM sleep in the second half of the night. - Improved sleep stability with a 5.3% reduction in cyclic alternating pattern (CAP) rate (p < 0.01) alongside higher subjective sleep quality. - A greater reduction in CBT (maximal difference of -0.28 °C). - A blunted rise in proximal back skin temperature (maximal difference of -0.98 °C). - A delayed rise in mattress surface temperature (maximal LHCM–HHCM difference of 6.12 °C). - Regression analysis identified proximal back skin temperature as the key variable predicting core-to-shell conductive heat transfer and SWS.
Why it matters
The findings demonstrate that enhancing conductive heat transfer via mattress thermal properties facilitates nocturnal core body cooling, directly increasing deep slow wave sleep and sleep stability.
Limits
The study had a very small sample size (n = 15) limited strictly to young, lean, healthy men, preventing generalization to women, older adults, or individuals with insomnia or thermal dysregulation. The intervention was evaluated under artificial laboratory conditions across single nights, leaving long-term adaptation and real-world durability unmeasured.