The fact that sleep is so sensitive to heat depends on how our internal biological clock is calibrated.
When the temperature drops, it sends a signal to the body that it is time to unwind and sleep, explains Christian Benedict.
It also helps the body cool down. This causes the blood vessels in the hands and face to dilate and release heat.
And it's important for us to sleep soundly. If it's over 20 degrees at night, like on tropical nights, it becomes very difficult. It makes sleep more elusive and fragmented.
Women tolerate heat less well
Some of us are also more vulnerable to heat than others, including the elderly and women.
The fact that women are more affected by the heat than men is partly due to the fact that men have more sweat glands, says Christian Benedict.
He believes that sleep will get even worse in the future if we don't do something radical - and he doesn't mean resorting to home remedies like putting your pillow in the freezer before going to bed.
Changes are needed at a societal level. We need to review the materials we use to build houses, how much asphalt we use, and ensure that we preserve more trees and vegetation.
A group of prominent sleep researchers raised the alarm this spring that the increasingly warm nights are already affecting the sleep of billions of people. At a sleep conference in Copenhagen this spring, they proposed the formation of a global working group to protect our sleep in an increasingly warm world.
According to their research, we are already losing the equivalent of 50 hours of sleep per year due to the heat, says Christian Benedict.
“No disaster”
However, he adds that the ongoing Swedish heat wave is unlikely to have any major consequences at the individual level.
It usually doesn't last that long and it's not a disaster to sleep poorly for a few days. We can handle it.
If you still want to help your body lower its temperature, there are some tricks, like taking a hot shower before going to bed.
The warm water helps the body cool down. Also remember to drink a lot, but preferably not right before you go to bed. Then you risk having to run to the toilet, says Christian Benedict.
Drink plenty of water but skip alcohol. It will make you sweat more and make it harder for your body to regulate its temperature.
Take a cold shower, but only during the day. Cold water constricts the blood vessels so they don't release heat. In the evening, a hot shower cools you down better.
Don't sleep naked. Sleeping completely naked puts you at greater risk of hypothermia. As sweat evaporates, your skin cools down.
Don't exercise late at night, it raises your body temperature.
Source: Christian Benedict, sleep researcher and professor of pharmacology at Uppsala University.
A scientific article by sleep researchers from the World Sleep Society and the International Pediatric Sleep Association shows that warm nights make us both fall asleep later and sleep for a shorter period of time.
Outdoor heat can cause sleep deprivation for several days, which can lead to sleep deprivation, even after the outdoor temperature returns to normal.
The researchers are calling for a global working group to gather knowledge and promote sleep health in an increasingly warm world.
The study, published in the journal Sleep, reviews more than a decade of research on the relationship between temperature and sleep.
