Make the bedroom cool and dark
A cool, dark, quiet room removes the signals that keep the brain in "day" mode.
Key takeaways
- What it is: A cool, dark, quiet room removes the signals that keep the brain in "day" mode.
- Why it works: Falling asleep requires a small drop in core body temperature, and a cool room helps the body shed heat to trigger it. Darkness matters because even modest light at night suppresses melatonin and lightens sleep. Removing heat, light, and noise lowers the arousal signals that compete with sleep onset and continuity.
- Evidence: Backed by observational / correlational evidence.
- Avoid: Leaving a TV, charging lights, or a bright clock visible — small light sources at night still nudge the clock and lighten sleep.
Why it works
Falling asleep requires a small drop in core body temperature, and a cool room helps the body shed heat to trigger it. Darkness matters because even modest light at night suppresses melatonin and lightens sleep. Removing heat, light, and noise lowers the arousal signals that compete with sleep onset and continuity.
How to do it
- 1Keep the room on the cool side — many people sleep best somewhat below normal daytime comfort.
- 2Block light with blackout curtains or an eye mask, and cover small device LEDs.
- 3Reduce noise with earplugs or steady background sound if your environment is loud.
What the evidence says
ObservationalThe drop in core temperature at sleep onset is well established, and laboratory studies show light exposure before and during sleep suppresses melatonin and disrupts sleep.
Honest caveat: Ideal temperature varies by person and bedding; the principle (cool enough to shed heat, dark enough to protect melatonin) is what holds.
- — Cho et al. (2016), effects of light at night on sleep and melatonin, Chronobiology International
Common mistake
Leaving a TV, charging lights, or a bright clock visible — small light sources at night still nudge the clock and lighten sleep.
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