Turn the Temperature Way Down

After earplugs and melatonin, if there’s one thing has made the biggest difference in my sleep, it’s having a cold room to sleep in – but it’s also been the most difficult change to make because our optimal sleep temperature is somewhere between 60 and 68 degrees Fahrenheit. That’s surprisingly cold. We usually think of room temperature as 72 degrees, so cooling your room another twelve degrees is hard. But temperature might be the most important sleep factor of all.

Light is often seen as the deciding factor in determining when humans fall asleep, but a convincing study in Current Biology has shown that temperature might be even more important. The researchers originally set out to determine how the artificial light that fills our lives affected our sleep. To compare modern humans with our ancestors, the scientists followed two isolated hunter-gather tribes, one in Bolivia, the other in Tanzania, and carefully documented their sleep patterns. Since these tribes had never encountered artificial light, they were the perfect comparison to us ‘modern’ humans.

Their findings were surprising. First, they realized that these tribespeople often slept less than seven hours a night but reported feeling well rested – even though their daily activity levels were similar to modern humans. Second, their sleep didn’t seem determined by sunrise and sunset – they stayed up for hours after sunset, just as we do, only they sat around a fire instead of a screen. Finally, the clearest environmental factor that matched their sleep patterns was not light but temperature. The tribes actually went to sleep once the temperature started dropping later in the evening and woke up as it began rising in the morning. Temperature!

This has been borne out by my own experience – I have my best sleep in a cold room with a lot of warm blankets… To consistently sleep in a cool room, however, I had to make some drastic changes. When I lived in Washington D.C., I lived in a beautiful townhouse but the master bedroom was on the top floor – super hot in the summer! Even with the AC on full blast it couldn’t cool the top floor, but of course cold air sinks so the basement was freezing. In desperation I moved the bed to the basement. Not the nicest surroundings, but the sleep was amazing. And it was really dark down there as well – two for one! Now I’m living in Europe and there isn’t much air-conditioning. I do have a ‘portable’ air conditioner though. It sounds like a jet engine and has to have an open window to exhaust hot air, which means you get the street noise. But even with all the noise (I have some good earplugs of course), my sleep is just much better when I’m in a cold room.


Make a Change

Do what it takes to get the room cold: open the window in the winter if you have to, turn the AC way down in the summer, sleep in the basement. It makes a difference!


References and Additional Resources

http://www.cell.com/current-biology/abstract/S0960-9822(15)01157-4 – Link to the study on pre-industrial sleep
http://well.blogs.nytimes.com/2015/10/15/112251/ – Story on the study and its implications

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