The Centers for Disease Control and Prevention (CDC) state that insufficient sleep is a serious public health concern, because it can lead to many immediate dangers such as car crashes as well as long-term health problems like diabetes. The blame for sleep deprivation is often pinned on our fast-paced, 24/7 lifestyle, made possible by electric lighting at all times of day and night.
But are we really getting too little sleep?
A new study challenges that idea from a unique perspective, and it is getting wide media attention.
Researchers, led by Jerome Siegel at UCLA, followed three small preindustrial societies, two in Africa and one in South America, reasoning that the best way to judge whether sleep habits in the industrialized world are unnatural is to compare them to sleep habits in those few remaining societies on Earth that still live without electricity. (Post continues after video.)
They found that the average period of time people spent trying to sleep was 7-8½ hours each night. Of this, only 5½-7 hours was confirmed as time asleep. This is about the same as, or less than, what is reported by most Americans and Europeans, and is considered too little for optimum health.
So maybe 5½-7 hours of sleep is natural and not the problem the CDC and many other health organizations say it is.
However, a crucial aspect of the findings of the new study has not been discussed in either the news stories or the paper itself: people in preindustrial societies spend much more time in darkness than people living in the industrialized world.
What does this study tell us about sleep patterns?
Besides finding that people in preindustrial societies without electricity sleep about the same amount as people in the electrified world, researchers also found that sleep didn’t start until several hours after sunset, although almost everyone woke up close to sunrise.
The researchers looked at temperature fluctuations, finding that it influenced the time of awakening in the morning. But for people sleeping in the modern built environment, temperature fluctuations in our bedrooms are minimal.
The researchers also found sleep in these societies was usually interspersed with periods of awakening that lasted for over an hour. These routine awakenings call into question the conventional wisdom that “ideal” sleep should be compacted into one stretch. Waking for a while at night is not necessarily a sleep disorder. Compacted sleep (“sleeping like a log”) is evidently not the way in which sleep evolved in humans.
But the big difference between sleep in the industrial world and sleep in the preindustrial world is about light and darkness. Electric light can delay or shut down nighttime physiology, whereas light from a wood fire or flame cannot. The researchers did not directly assess the quality of sleep, and this may be the part that matters. (Post continues after gallery.)