Sleep · Protocol 5 of 15
Keep your bedroom cool at night
1In 30 seconds
Keep your bedroom cool, warm your hands and feet with a hot shower or wash before bed, and let your feet poke out from under the covers. Your body needs to cool down by a degree or so to fall asleep, and this helps it get there.
2Picture it
3Why do it
- 1
You will fall asleep faster, because a cooling body is one of the main signals that it is time for sleep.
- 2
You are likely to stay asleep longer and get more deep sleep, instead of waking up hot and restless.
- 3
It costs little or nothing and can feel like a calming bedtime ritual.
4How to do it
- Aim for a bedroom temperature of about 18 to 20°C, and no warmer than about 21°C if you can manage it.
- Before bed, warm your hands and feet with a hot shower or bath, or even by washing your face with very warm water.
- Loosen the sheet around the bottom and edges of the bed so your hands and feet can easily slip out into the cool air.
- Skip socks in bed, particularly if night waking is a problem for you. If you always feel very cold, you can ignore this step.
- Avoid hard exercise in the 3 to 4 hours before bed. Moderate or hard exercise in the early or middle afternoon may help your sleep instead.
5Make it work in India
- Few Indian homes can run the AC at 18 to 20°C, and it is costly. Set it to the lowest temperature you can comfortably afford, run a ceiling fan with it, and use the timer so it is coolest in the first half of the night.
- Without AC, use cotton bedsheets, a light dohar instead of a heavy quilt, and open windows on opposite sides for a cross breeze. Bengaluru nights are often naturally cool enough with an open window.
- In hot weather, a lukewarm bath rather than a very hot one still warms your skin enough to trigger the cooling effect afterwards.
6The long read: the science2 min read · tap to open
Your core body temperature rises through the morning, peaks in the afternoon and then slides down in the evening. To fall asleep, it needs to drop by about half a degree to a degree Celsius. Interestingly, the speed of the fall seems to matter as much as how low it goes. People tend to head for bed just as their temperature is dropping fastest.
The cooling and the sleep hormone melatonin work as a pair. As your temperature falls, melatonin rises, and the coolest part of your night lines up with your deepest sleep. Research suggests a room of roughly 19 to 21°C works well for most people. That keeps the thin layer of air right next to your skin at about 31 to 35°C.
Your body sheds most of its heat through the skin of your hands, feet and face. As you relax, your nervous system shifts into calm mode and sends more blood to these areas, where heat escapes. That is why sticking a foot out of the blanket can feel so good.
Why would a hot shower help, when the aim is to cool down? A warm-up of the skin is noticed by a part of your brain that acts like a thermostat. It responds by opening up those heat-release channels, and your core temperature drops afterwards. Scientists call this the warm bath effect. Hard exercise late at night does the opposite. It raises your core temperature right when you want it falling.
Good evidence Research consistently links a cooler room and a warm bath or shower before bed with falling asleep faster, though the ideal settings vary from person to person.
Questions people ask
I can only exercise at night. Should I skip it?
No, exercising late is better than not exercising. Help yourself wind down afterwards with a warm shower, slow breathing with long exhales, dim lights and no caffeine after 1 or 2 p.m.
I like heavy blankets. Is that wrong?
Not at all. Many people sleep well in a cool room under warm covers. Just let your feet or hands stick out so your body can still lose heat.
7Be careful
If you have diabetes, poor circulation or numb feet, test bath water with your elbow and avoid very hot water. Older adults, babies and people who feel the cold easily should not be kept too cold; keep them comfortable rather than chilly.
8Try it for 7 days
Tap a day each time you cool room, warm wash.
From the book: “Lower Your Core Body Temperature at Night” (Sleep Protocol 5). Evidence rating and India notes are our own.