Core Temperature & Sleep
topic
Core body temperature follows a circadian cycle that peaks in the late afternoon (facilitating alertness and physical performance) and drops by approximately 1–2°C in the evening and overnight — with the drop itself being a physiological signal that initiates sleep and facilitates slow-wave sleep. Sleeping in a cool environment (18–19°C / 65–67°F) facilitates this temperature drop by enabling heat loss through the skin, while warm environments prevent the drop and measurably degrade slow-wave sleep quality.
Role
Bedroom temperature is one of the most impactful and most overlooked sleep environment variables — yet most people have never been told the specific temperature range that optimizes sleep quality or the mechanism through which temperature affects sleep physiology. The person who drops their bedroom temperature by 4–5°C from the typical indoor temperature of most developed-world homes consistently reports improvements in sleep depth, ease of falling asleep, and morning energy — improvements that require no supplements, no devices, and no behavioral change other than adjusting a thermostat.