Passive Body Heating

How does core body temperature effect sleep?

The brain regulates your sleep cycles to the pattern of day and night. That’s why light and dark affect sleep and wakefulness. Part of this natural day/night cycle is temperature- warmer in the daytime and cooler at night. That means that how warm or cool your body temperature will effect whether you feel sleepy or awake.

When we fall asleep our body temperature naturally drops. If the environment is too warm or we have too many blankets or too much heavy clothing on we will not be able to have a deep, restorative sleep.

Passive Body Heating can help you send your body a message that it is time to go to sleep. It works by first raising the body’s temperature (a warm bath or shower, an electric blanket, or holding a hot water bottle in your lap) all help raise your body temperature. Once you take away that heat source your body temperature will drop. When it drops your brain interprets this as a signal that it is time to go to sleep.

Passive Body Heating

Passive body heating works by increasing the core body temperature followed by rapid cooling. This should be done 60-90 minutes before the desired bedtime.

How does it work?

When we sleep our body temperature drops slightly. Being too warm keeps us from going to sleep. If you raise a person’s core body temperature slightly for a short period while he is awake, as his core body temperature drops he will feel sleepier.

That is why a warm bath before bed helps us sleep- the bath raises our core body temperature for a short period and as we cool off after the bath we feel sleepy.

Research has found that a warm bath or shower 60-90 minutes before bedtime promotes better quality of sleep.

What should you use for passive body heating?

Different people have different activities they will tolerate or enjoy in the evening. You may have to experiment a bit.

Some suggestions to promote passive body heating:

  • A warm bath or shower
  • A hot water bottle held in the lap or used as a back cushion
  • A warm ‘wheat bag’ wrapped around the shoulders. These are available in pharmacies and some gift stores, you heat them in the microwave. They are safer and easier to manage for some people than a hot water bottle or an electric heating pad.
  • An electric blanket (you should set this on a timer to go off after 30 minutes). The electric blanket needs to turn off after 30 minutes or you will not cool off and achieve a drop in core body temperature.

Remember- the heat source has to first raise core body temperature but then it must cool off. It is only when core body temperature drops that the brain gets a message that it is time for sleep. Caution – Remember the warmth should be comfortable, not hot and unpleasant.

More information about passive body heating:

Talk to an occupational therapist or other healthcare provider for simple suggestions about how to use passive body heating.

Read more about passive body heating in the research study by Mishima et al (2005) Passive Body Heating Ameliorates Sleep Disturbances in Patients With Vascular Dementia Without Circadian Phase-Shifting. American Journal of Geriatric Psychiatry: Volume 13 – Issue 5 – p 369-376

Advice from WebMD about bedroom temperature

Watch a short video on sleep and body temperature by Dr John Winkelman, M.D., Ph.D. Assistant Professor of Psychiatry, Harvard Medical School and Medical Director Sleep Health Center of Brigham Hospital

Information on this page contributed by Cary Brown