Six hours' sleep a night is enough, say scientists

Findings from research published this week show modern humans get no more or less sleep than their ancestors did 

Hardeep Matharu
Friday 16 October 2015 09:00 BST
A new study suggests that people in modern societies are getting enough sleep
A new study suggests that people in modern societies are getting enough sleep

Getting an average of six hours’ sleep is no less shut-eye than our ancestors had, a new study has suggested.

Although long working hours, television and the internet are blamed for reducing modern sleep times to supposedly unhealthy levels, findings in a new study suggest that people living in primitive societies do not get any more or less sleep than those living in “industrial” societies.

The study, published in the Current Biology journal this week, was conducted by researchers at the University of California Los Angeles’ Semel Institute of Neuroscience and Human Behaviour.

It examined sleep and how it varied in three “pre-industrial societies” in which traditional lifestyles mirror those of our ancestors more closely.

The study aimed to test the assumption that reduced sleep time in the modern world is linked to obesity, mood disorders and other mental and physical illnesses.

1,000 days’ worth of data was collected from 94 adults living in the Hadza society in northern Tanzania, the San in Namibia, and the Tsimane people in Bolivia. In all three societies, people live nomadically, dependent on hunting and gathering food.

But the study found that the average sleep time in these societies was 5.7 to 7.1 hours, with an average of 6.4 hours a day – not significantly more than those living in modern societies.

It also found that adults living in the pre-industrial socities had lower levels of blood pressure and higher levels of physical fitness.

The study said: “By examining three such groups in two continents over long period of time, we were able to evaluate common elements and differences that provide insights into the nature of human sleep under natural conditions.

“A striking finding is the uniformity of sleep patterns across groups despite their ancient geographic isolation from each other.

“This suggests that the observed patterns are not unique to their particular environment or cultural conditions but rather are central to the physiology of humans living in the tropical latitudes near the locations of the San and Hadza groups, where our species evolved.

“The sleep in these traditional human groups is more similar to sleep in industrial societies than has been assumed. They do not sleep more than most individuals in industrial societies.

“Sleep occurs almost entirely during the dark period in these traditional societies. In contrast, sleep typically continues well after sunrise in industrial populations.

“Our findings indicate that sleep in industrial societies has not been reduced below a level that is normal for most of our species’ evolutionary history.”

According to Jerome Siegel, one of the study’s researchers, the findings are significant in challenging assumptions that people in the modern world need more sleep.

He said: “The short sleep in these populations challenges the belief that sleep has been greatly reduced in the modern world,” reports Science Recorder.

“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.”

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