It turns out that a warm bath or shower isn't just a cleansing, relaxing bookend to a long day. There's real science behind the benefits of bathing at night to promote and improve sleep—particularly when it's timed just right.
You may already know that taking a warm bath or shower (scientifically referred to as water-based passive body heating) before bed can help you fall asleep and stay asleep. A sleep study conducted by researchers at the University of Texas, not only verifies that recommendation but digs into exactly how and when to bathe before hitting the sheets for optimal Zzzs.
The Science Behind Passive Body Heating and Sleep Quality
Researchers combed through more than 5,000 published studies on the effects of water-based passive body heating on sleep quality, length, efficiency, and onset latency (or, how quickly it takes you to fall asleep)—and found that the ideal pre-snooze bathing routine looks like this:
"[Water-based passive body heating] of 40 to 42.5 degrees Celsius (about 104 to 108.5 degrees Fahrenheit) was associated with both improved self-rated sleep quality and [sleep efficiency], and when scheduled one-to-two hours before bedtime, for little as 10 minutes, led to significant shortening of [sleep onset latency]."
Translation: Take a 10- to 15-minute, warm (but not too hot) shower or bath one to two hours before going to bed to help you fall asleep more quickly and stay in a deep, restful sleep through the night. Why? While taking a cold shower has its own merits, a warm shower or bath will first increase your body temperature, after which your body will experience an even more pronounced decrease in body temperature—that temperature dip is what promotes sleep.
Adding a Bath or Shower to Your Nighttime Routine
If you're not sure whether it's best to shower in the morning or at night, or you're prone to restless nights and insomnia, you should absolutely give this (free and familiar!) sleep trick a try you may already be doing it without realizing.