A small trial that builds on earlier evidence
STUDY: Stevenson S et al, Temperature 2026
STUDY TYPE: Non-randomized, parallel-group field study
FUNDING: Independent
Background
Temperature is a circadian signal, and hotter nights worsen sleep. Cooling mattresses are marketed to improve sleep, and this study tested them in elite athletes.
The Study
- 32 elite male Australian-rules football players, mean age 23, in pre-season training.
- Assigned by device availability, not randomly: 16 slept on a temperature-controlled cover, 16 on their own mattress, each 14 or more nights.
- Outcome: sleep on a modified 2-week Pittsburgh Sleep Quality Index (B-PSQI), plus thermal comfort ratings in the cover group.
Total sleep time rose 29 minutes with the cover, versus almost no change with usual mattresses (effect size 1.41), ending 43 minutes ahead of controls. Sleep quality and B-PSQI scores also improved more with the cover, though that group started with worse baseline sleep.
Thermal comfort didn’t change, suggesting the effects of temperature are not related to conscious sensation. Sleep latency, disturbances, and efficiency didn’t differ.
Limitations
Non-randomized, non-blinded. The cover group’s worse baseline sleep raises the chance of regression to the mean rather than a device effect.
Practice Implications
- Like light, temperature sets the biological clock. People with insomnia should sleep in a colder room (60-65 degrees F), and program the thermostat to warm up in morning.
- A cooling mattress is another method, and other small trials show they help people fall asleep faster and increase slow-wave sleep, particularly in women with menopausal vasomotor symptoms.
- Most devices studied circulate water or air to cool through the mattress, a topper/pad, or pillows. I wrote about Airweave in the Depression and Bipolar Workbook, a pad that deepens sleep by creating space for airflow between the body and the mattress:
—Chris Aiken, MD
Director, Psych Partners
Editor in Chief, Carlat Psychiatry Report
