Before the clocks change: the 90-minute warm water rule

Daylight saving starts this Sunday, 4 October, in South Australia, New South Wales, Victoria, Tasmania and the ACT. We lose an hour, and many of us lose a few nights of good sleep with it.

Here is one habit with solid evidence behind it.

The research

Biomedical engineers at the University of Texas at Austin reviewed more than 5,000 studies on warm water and sleep, published in Sleep Medicine Reviews in 2019. Thirteen had comparable data for pooling.

They found that a warm bath or shower at 40 to 42.5 °C, taken one to two hours before bed, improved self-rated sleep quality and sleep efficiency.

Sessions as short as ten minutes helped people fall asleep faster, by about ten minutes on average.

Why it works

Your core temperature naturally falls in the hours before sleep. Warm water draws blood to your hands and feet, which helps you shed heat faster afterwards. The cooling curve arrives on time, and sleep follows.

How to use it

• Aim for about 90 minutes before bed.
• Ten to twenty minutes is plenty.
• Keep the bedroom cool afterwards.
• Start this week so the habit is in place before the clocks change.

With Norge

The N-02 heats as well as chills, up to 40 °C. That is the lower edge of the studied range, so it is a gentle option rather than a hot bath.

An evening session in the Stillhet Kube, finished well before bed with a gradual cool down, works on the same principle.

Free: The Norge Longevity Guide. Heat, cold and light after 50, with the evidence and the safety rules in one place. Get the guide.

Sources

1. Haghayegh et al., Before-bedtime passive body heating by warm shower or bath to improve sleep, Sleep Medicine Reviews, 2019
2. UT Austin news release

This article is general information, not medical advice. If you have a heart condition, low blood pressure or are pregnant, speak with your GP before using heat or cold.