How does sleeping in a hot room impair brain function? New findings from scientists

14 November 2026, 22:572 min read0

The hotter the room you sleep in, the slower your thinking will be the next day. Scientific studies have shown that each additional degree of heat increases the risk of "brain fog" (clouded thinking) and difficulties with concentration. This is not even about extremely high temperatures — the average temperature in the bedrooms of the study participants was approximately 24°C (75°F).

How does this process occur?

Sleeping in a hot room disrupts sleep quality and reduces the brain's processing speed, memory, and concentration ability the next day. This is caused by the following factors:

Obstruction of body temperature drop: For a person to fall into deep sleep, the body's internal temperature must drop by approximately 1°C. If the room is hot, the body cannot dissipate heat, and sleep becomes shallow.
Reduction of brain recovery phases: High temperatures shorten the deep sleep and REM (rapid eye movement) phases, during which the brain rests and consolidates memory. As a result, the brain does not fully recover by morning.
Decline in cognitive abilities: In an experiment conducted by Harvard scientists, students who slept in a hot room without air conditioning (average 26°C) performed 13% worse on logic tests the next day compared to those who slept in a cool room (21°C). Specifically, making quick decisions and performing complex tasks became more difficult.

Sleep temperature and its impact	Indicators and details
Optimal temperature	16°C — 19°C (sometimes 20–21°C) for healthy adults
For the elderly	Slightly warmer temperature (around 20°C–23°C)
Result of the Harvard experiment	Those who slept in a hot room scored 13% lower on logic tests

Practical recommendations for quality and healthy sleep

To ensure your brain works clearly and alertly in the morning, it is recommended to follow these rules:

Ventilating the room: Open the window 15–20 minutes before sleep to let fresh and cool air into the room.
Using natural fabrics: Instead of synthetic sheets and clothing, choose breathable cotton or linen fabrics.
Warm shower before sleep: Taking a warm, not hot, shower dilates the blood vessels on the skin's surface. After getting out of the shower, the body cools down faster, making it easier to fall asleep.

Do you pay attention to the room temperature while sleeping? What methods do you use to keep the room cool? Leave your thoughts in the comments!