Sleep patterns in pre-industrial communities highlight the importance of temperature changes
What is the connection between insomnia and the modern lifestyle? It has been hypothesized that we sleep less well now than our ancestors did, either because of electric lighting, electronic devices, or increased entertainment options. However, a group of scientists studying sleep patterns among members of hunter-gatherer tribes in present-day tropical climates have made some surprising findings.
Using wristband monitoring devices, researchers studied sleep and waking patterns among people living in preindustrial societies without electricity or indoor heating or air conditioning. In three widely separated areas, two in sub-Saharan Africa and one in Bolivia, people slept for an average of 5.7 to 7.1 hours per night. They did not regularly awaken for extended periods in the middle of the night, and none of the groups had a word for “insomnia” in their language. After explanations provided by translators, less than 3% of the participants reported regularly experiencing sleep problems.
The general pattern was that people went to sleep about three hours after sunset and awoke as much as an hour before dawn. Seasonal variations showed nearly one hour difference in sleep time between summer and winter, that is, people slept longer when the weather was colder. Because they went to sleep later in the summer months, those who lived furthest from the equator (and therefore had a greater difference in light times between summer and winter) would wake after sunrise in the summer, leading the researchers to posit that light timing and exposure was not the determinant factor in sleep patterns.
Ambient temperature appeared to be the most important determinant of waking time, with “onset” of waking beginning at the lowest temperature of the night (just before dawn). Participants also did not begin to sleep early in the night, just after sunset, but only about three hours later, when the temperature lowers.
These results suggest that we pampered industrial-society sleepers should look seriously into some way of modifying the ambient temperature in the rooms where we sleep, either by some kind of programmable space heater or furnace, or by sleeping with the window open. While early morning light has also been shown to be an important aid to sleep management, we are just beginning to explore the role of room temperature in sleep.
We have had some experience with devices that help regulate temperature. One of the people in our clinic has had a good experience with the Ebb device, which regulates forehead temperature and is and FDA approved treatment for insomnia. We are going to be writing a more comprehensive review of the device in the next couple of months. Another device is a mattress pad that does the same thing, made by chilisleep. That device is not FDA approved and is quite expensive but should be helpful for insomnia.
Yetish, G. et.al. Natural Sleep and Its Seasonal Variations in Three Pre-industrial Societies. Current Biology. Report| Volume 25, ISSUE 21, P2862-2868, November 02, 2015. Open Archive Published: October 15, 2015 DOI:https://doi.org/10.1016/j.cub.2015.09.046