Sleep experts generally recommend a room temperature of 66-70 degrees Fahrenheit as being optimal for sleep. If you’ve tried this, you’ve probably found that it certainly isn’t far from the mark; most people sleep alright at that temperature range.
On the other hand, if you have trouble sleeping, you’ve probably found that simply setting your thermostat to 68 doesn’t solve the problem (or sometimes it seems to, while other times it doesn’t).
And, of course, if you have an inquisitive mind, you might be asking, shouldn’t it depend on the temperature during the particular day? After all, people in the tropics don’t all have insomnia.
What the research actually suggests is that this 66-70 degree range is a good starting point, but there’s a lot more going on with sleep temperatures that you need to consider.
What's the Best Temperature for Sleeping?
Body temperature is indeed a major regulator of sleep, and — as logic would dictate — your body should be significantly cooler at night than it is during the day. In fact, higher temperatures are associated with more sleep disruption on a population level, which probably won’t surprise anyone who’s experienced a heat wave.
On the other hand, insomniacs (especially older ones), may actually sleep better if their skin is warmed up by 0.4 degrees Celsius (0.7 degrees Fahrenheit). Curiously, this skin warming does not increase core body temperature, as the body seemingly slows its metabolism to compensate. This suggests that insomniacs may have trouble sensing the optimal sleep temperature and adjusting their sleep environment accordingly.
It is, of course, also true that you have to take personal comfort into account. Any temperature that feels uncomfortable is automatically going to be a problem.
Although not tested, it is very likely true that the optimal temperature for sleep is actually relative to the temperature during the day. If it was 90 degrees during the day, 72-75 might be ideal for sleep, while during cold winters, 60-64 might feel better.
In fact, the optimal sleep temperature may be relative not only to daytime temperature, but to the temperature just a few minutes earlier.
Sleep Temperature: Why It's All About Timing
Quite a few studies now suggest that what matters is not merely your body's temperature when you sleep, but the rate of temperature change.
Taking a warm bath or shower before bed can greatly shorten sleep onset times and help you get into a deeper sleep earlier in the night. It seems to be not the bath itself, but the rapid cooling afterward that causes this.
Further studies suggest that sleep may be related not merely to ambient temperature, but to a variety of thermoregulatory behaviors that serve to adjust core body temperature. Sleep is associated with a lower core body temperature regardless of ambient temperature, but sometimes this actually correlates with increased skin temperature as the body sheds heat more effectively.
In fact, one study found that non-REM onset is most likely when core body temperature is declining the fastest. It is the rate of decline, more so than the absolute temperature, that seems to matter.
What all of this suggests is that you should aim for 66 degrees Fahrenheit during sleep onset, which is in line with common wisdom. But more importantly, you should try to rapidly plummet your body temperature shortly before bed, rather than gradually cooling it down.
You can do this by taking a warm shower before bed and allowing yourself to be cold as you dry off. Alternatively, you might set your air conditioner to run at full blast until shortly after bedtime, then turn it down or off entirely. Finally, you could simply open your windows on a cold night, only to close them shortly before bed, replacing them with a gentle fan for continued cooling.