It’s a little weird for me to become an advocate for air conditioning. But I’ve come to really appreciate the importance of sleeping cool.
Let’s start by agreeing that sleep is far more important to health than many give it credit for. It’s fundamental on every axis that matters, from mind to mood to heart to hormones to immunity and income — and even staving off death.
I write that list quickly, but the more you know about how sleep actually functions, the madder you’ll get that our society actively undermines it. (Learn more in the fascinating book, Why We Sleep, by Matthew Walker. He’s a sleep scientist, and he does get mad.)
(For those of you in the herbal community, you’ve likely heard we lost John Gallagher, one of our own, to insomnia, anxiety and depression. There’s a bidirectional relationship between mood and sleep, each making the other worse — or better, with successful treatment. But understand that insomnia is explicitly part of what led to John’s death.)
sleeping cool matters
Scientists find that sleeping cool, within limits, makes a big difference in almost every important parameter of sleep. A hot bedroom will worsen:
- total sleep time
- sleep efficiency (the percentage of time in bed you’re actually asleep)
- how much you dream, and
- how long you spend in deep sleep.
The elderly and folks with lower incomes are at greatest risk.
new research highlights the harm of heat
And a new study, published last week in Nature Communications, found that increasing temperatures also significantly increase risk of obstructive sleep apnea.
Apnea is the condition where people stop breathing repeatedly through the night, leading to mini-awakenings that prevent effective sleep. And apnea is hugely under diagnosed: An estimated 30 million people in the U.S. and 1 billion worldwide have the condition — and 80 percent are undiagnosed. Risk factors include snoring, perimenopause and menopause, and being overweight.
And let me be clear: untreated sleep apnea doesn’t just leave you tired and vulnerable to all the ill effects of inadequate sleep. Untreated sleep apnea shortens life.
The researchers looked at 125,000 people in 41 countries and found that temps above 80ºF raised the average risk of sleep apnea by 50 percent, and severe sleep apnea by 40 percent. But those are average numbers. In some countries, the risk rose by 200 percent — and the researchers believe this relates to access to air conditioning.
how hot is too hot?
Most researchers, along with institutions including the Cleveland Clinic, put optimal bedroom temperature between 60 to 67 degrees Fahrenheit.
For perspective: Until I got air conditioning upstairs a few years ago, on hot nights it was impossible to get my bedroom temperature below 80ºF before 2 am using a fan alone. I don’t love air conditioning for many reasons, but at a certain point room cooling isn’t just about comfort, it’s actually treatment.
Individuals may find their optimals vary. But if you think you sleep well at temperatures that are significantly higher or lower, try sleeping in this range and see if you get better rest.
when a/c is not an option
What are some other ways to cool down for bed when it’s too hot to sleep?
Fans can help, even if air temps are too hot. Try putting on a damp t-shirt, or using damp sheets, and training a fan on your bed. The evaporation will help you cool down. Another option is keeping your sheets in the freezer until bedtime.
You also can find expensive water-cooled mattress toppers, which some folks swear by. I tried this one and hated it; it just didn’t work for the way I sleep.
Although it may seem counterintuitive, a hot bath two hours before bed can help you cool down. When your body is hot, it shunts blood to the surface and extremities where it can more easily offload heat. When you get out of a hot bath, that contrast will help drop your core temperature to improve sleep. In one study of this tool, participants saw improved sleep quality, sleep efficiency and shorter times falling to sleep.
Find more suggestions for sleeping in heatwaves from the European Insomnia Network.
If you’d like to dig into the subject of heat and sleep, I’ve gathered a bunch of news reports, public guidance and research studies as part of the Naturopathic Climate Alliance. You can find the growing list here.
Wishing you the best rest,
—Dr. Orna
