Does a sauna help you sleep?

What is the evidence?

The main source is the Global Sauna Survey, an online questionnaire of 482 regular sauna users, most of whom used a sauna once or twice a week. Of all respondents, 83.5% said they slept better after a sauna.

That is a high number, but it comes with big caveats:

• The people who answered were enthusiasts who chose to use saunas regularly.
• Nobody measured their sleep.
• There was no comparison group.

A systematic review of clinical studies of regular dry saunas did not find any good-quality trials that measured sleep as the main outcome. So we grade the evidence as weak.

Why might heat help you sleep?

Your core body temperature naturally falls in the evening, and that fall is one of the signals that helps you fall asleep. Warming up in a sauna widens the blood vessels in your skin. When you come out, they keep shedding heat, so you cool down faster. Research on warm baths and showers before bed points the same way. It’s a sensible theory, but it hasn’t been tested for saunas.

How should you use a sauna if you want to try it?

• Finish your session one to two hours before bed, so you have time to cool down.
• Drink water afterwards, but not so much that you’re up in the night.
• Skip alcohol, which is risky in a sauna and worsens sleep.
• If you like a cold plunge, keep it short in the evening.

If you have had trouble sleeping for months, a sauna is unlikely to fix it on its own. Speak to your GP about CBT for insomnia, which has good evidence.