Sleep update: some new information

I have written several posts about sleep (see the Topics menu for a list), the gist of which is not to worry if you don’t get eight hours of uninterrupted sleep. New research, published in Current Biology, underscores that message and adds new information.

Researchers studied the sleep habits of three hunter-gatherer societies, two in Africa (The Hadza and San tribes) and one in Bolivia (the Tismane people). These tribes live much as their ancestors have for tens of thousands of years. By studying these people, the researchers could determine how early humans were “programmed” to sleep, and, by extension, what normal sleep might be for us. (Of course, manufacturers of Ambien and Lunesta would have you believe that less than eight hours of sleep will have dire consequences.) Like early humans, the hunter-gatherer people sleep outside or in crude huts and their only light at night comes from fire.

What the researchers found is that, on a typical night, these people sleep slightly less than the average American. In the US, most adults sleep seven hours or more a night--although many sleep significantly less. Members of these hunter-gatherer tribes slept just six and a half hours. About like me. Researchers also found that the presence or absence of daylight is not the primary factor in their sleep patterns.

The conventional thinking has been that the artificial light throws off our biological clocks and that if we could live like early humans, going to bed when the sun goes down and getting up when the sun comes up, we’d be much better off. It turns out that the people in all three of these tribes do not follow that sundown/sunup scenario. Instead, they stay awake several hours after the sun goes down and do not wake at sunrise. What does determine their sleep habits is temperature. They almost always fall asleep as the temperature begins to fall at night and wake up as the temperature rises in the morning. This habit suggests that humans may have evolved to sleep during the coldest hours of the day, perhaps as a way to conserve energy.

From what I can observe, most of us modern humans like sleeping in a cool bedroom. In the 20 years we have lived in our house, we have never turned the heat on in our bedroom (it has its own heat zone). We also open windows at night. Most people I know do the same thing. We seem to have figured it out ourselves.

Next week: A dose of radiation for health?

For an introduction to this blog, see I Just Say No; for a list of blog topics, click the Topics tab.