Found a New York Times article describing a study in which researchers compared the sleep patterns of three different groups of tribal populations; the Hadza and San tribes in Africa, and the Tsimané people in South America. All three groups represent prehistoric tribal populations and all three are found to sleep fewer hours than contemporary Americans.

These findings are of interest as concern has been raised over the pace of modern life and the prevalence of a wide variety of electronic devices from cell phones to tablets all of which serve to disrupt personal schedules and allow bringing the office into the home. In addition to electronic devices, industrial man has the benefit of round the clock lighting and is therefore able to undertake activity that would have been unlikely, if not impossible, in a preindustrial era.

The sleep hygiene of the three hunter-gather groups under study all exhibited the same pattern. They began sleep three to four hours after sunset and would wake an hour before sunrise. The onset of sleep was associated with a decline in ambient temperatures. Waking occurred at the point the daily ambient temperature was at its nadir. The sleep period ran from 7 to 8.5 hours a night. Members of the groups under study rarely took naps during the day. They did not break the sleep period into two separate intervals but maintained an unfragmented sleep period.

Of considerable interest is the fact of the similarity in sleep patterns between the three groups despite the great geographic separation between them:

“The Hadza and the San live in the area where we know humans evolved, and then the Tsimané live in some sense at the end of the human migration,” he said. “The fact that we see very similar sleep times gives me great confidence that this is how all of our ancestors slept.”

Their sleep did not seem to be problematic. Chronic insomnia, which affects 20 percent to 30 percent of Americans, occurred in just 2 percent of the hunter-gatherers. The San and the Tsimané did not even have a word for it in their languages.

This information provides a useful basis on which to undertake an attempt to stabilize my own sleep habits.

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The New York Times article may be found here.

The full study is found here.