In an effort to uncover how humans might have slept before the modern age of industrialisation and artificial lighting, Dr Jerome Siegel and colleagues travelled to remote corners of the globe to study three of the last remaining primitive hunter-gatherer societies left on earth; the Hadza of Tanzania, the San of Namibia, and the Tsimane of Bolivia.
To record their sleep patterns, researchers fitted each individual with an Actiwatch 2 – a medical-grade wrist worn sleep tracker.
Conventional wisdom assumes that human sleep patterns evolved in tandem with the natural cycle of light and dark. But when Siegel and his team got the results back, he found no such correlation.
Despite their geographical distance the groups showed remarkably similar sleep patterns. They found that on average, the three groups:
The guidelines stated that “Sleeping less than 7 hours per night on a regular basis is associated with adverse health outcomes, including weight gain and obesity, diabetes, hypertension, heart disease and stroke, depression, and increased risk of death.”
According to these guidelines the hunter-gatherers should all have been suffering chronic health problems. Siegel’s study however found the opposite. By Western standards all of the tribe members were in very good health.
These ‘short-sleeping’ hunter-gatherers had higher levels of physical fitness, lower BMI’s, lower blood pressure and better heart conditions than Westerners.
So what explains the discrepancies? One of the reasons, according to Jim Horne, director of the Sleep Research Centre at Loughborough University, UK, is that sleep quality may be much more important than sleep quantity. Speaking to the New York Times he said:
“There is this concern in the Western world that we need more sleep and that if you get less than seven hours you’re liable to suffer from obesity and diabetes and heart disease. But the average amount of sleep in these people was well under what is recommended to us as adequate sleep, and these were very healthy people who are not suffering chronic disease and insomnia.”
Dr Siegel said the findings were significant for those who feel they’re not getting the recommended amount of sleep. Talking to the Washington Post he said
“The short sleep in these populations challenges the belief that sleep has been greatly reduced in the ‘modern world.’ This has important implications for the idea that we need to take sleeping pills because sleep has been reduced from its ‘natural level’ by the widespread use of electricity, TV, the Internet, and so on.”
John Peever, a sleep expert at the University of Toronto also remarked that the results could potentially shake up the way we currently perceive what is ‘normal’ sleep and our current understanding of sleep deprivation in Western societies. He said:
“I think this paper is going to transform the field of sleep… It’s difficult to envision how we can claim that Western society is highly sleep deprived if these groups that live without all these modern distractions and pressing schedules sleep less or about the same amount as the average Joe does here in North America.”