Manipulating core body temperature by warming hands, feet, or the core can induce sleep more quickly and increase deep sleep by 10-20%.

“Furthermore, increasing core body temperature before sleep can be beneficial. This is a credible finding, as it has been shown to decrease sleep latency by activating thermoregulation circuits that facilitate faster cooling and initiate sleep more quickly.”

“And lo and behold, when they dropped the core body temperature, they were able to induce sleep quicker, and the amount of deep sleep, what we call slow-wave sleep, which is deep non-REM sleep or Stages 3 & 4, also called slow-wave sleep because of these big powerful slow brainwaves, that deep, rich non-REM sleep was increased somewhere between about 10% to 20%, which is non-trivial.”