Sleep optimization

Sleep comes most easily as the body's core temperature falls. Six daily practices, temperature first, and what the research found.

1. A cool bedroom.

   A review found that in real-life conditions, with bedding and clothes, heat increased waking and reduced both slow-wave and REM sleep (Okamoto-Mizuno and Mizuno, 2012).¹

2. Warm shower or bath, one to two hours before bed.

   A meta-analysis linked water at 40 to 42.5 °C to better self-rated sleep and sleep efficiency, and, one to two hours before bed, to falling asleep faster. No clear effect on deep sleep itself, and the authors call the research scarce (Haghayegh et al., 2019).²

3. A bed that cools and warms, for comfort.

   In a small randomized trial of 34 healthy adults, funded by a university rather than the maker, a mattress cover that cooled or warmed the bed through the night made sleep feel much better, yet sleep measured at the wrist, and heart rate, did not change. Sleepers knew when it was on, and the authors say expectation may explain part of the gain (Stevenson et al., 2025).³

4. Hard sessions, finished over an hour before bed.

   Across 23 studies in healthy adults, one evening session slightly raised slow-wave sleep, by about 1.3 percentage points. The authors caution that vigorous sessions ending within an hour of bed might delay sleep and cut its length and efficiency (Stutz et al., 2019).⁴

5. Seven hours, at least.

   The American Academy of Sleep Medicine and the Sleep Research Society advise adults to sleep seven or more hours a night on a regular basis (Watson et al., 2015).⁵

6. No nightcap.

   A review of studies in healthy volunteers found that, at every dose, alcohol consolidated the first half of the night, then disrupted the second half and delayed the first REM period (Ebrahim et al., 2013).⁶

The bed is yours. The rest, handled at your house.