Do We Really Need 7-8 Hours of Sleep a Night?

According to the Centers for Disease Control and Prevention (CDC), Americans face a hazardous public health problem—too little sleep! The CDC recommends 7-8 hours of sleep a night, a guideline that’s backed by the American Academy of Sleep Medicine and the Sleep Research Society. Insufficient sleep has been tied to health conditions such as weight gain, obesity, diabetes, heart disease, high blood pressure, stroke, depression, and an increased risk of death. Despite these risks and recommendations, 1/3 of Americans sleep fewer than 7 hours a night. A new study, however, suggests that 7-8 hours of sleep a night may not be necessary for optimal health.

woman_sleepingPerhaps You’re Not As Sleep Deprived as You Think

Some experts estimate that Americans sleep 2-3 hours fewer than we did before the Industrial Revolution and the advent of artificial light and digital technology. Computers, smartphones, and television are cited as the primary culprits of insufficient sleep. Sleep experts believe that artificial light from screens and lamps disrupt our circadian rhythm and block the release of melatonin, which brings on sleepiness.

New research published in Current Biology suggests otherwise. Researchers tracked the sleep patterns, light exposure, and temperature exposure of 3 hunter-gatherer societies: the Hadza and San tribes of Africa, and the Tsimané of South America. Analysis showed that all three tribes slept similar amounts (and slept through the night instead of at intervals), despite their geographical distance. The 6½ hours of sleep the hunter-gatherers clocked in on average is fewer than the 7 hours Americans sleep on average.

The hunter-gatherers were also assessed as relatively fit and healthy. Previous research suggests that they aren’t any more physically active than Americans on average, so researchers have ruled out movement as the driving factor in hunter-gatherer health.

Hunter-gatherers either slept outside or in makeshift huts and went to bed 3-4 hours after nightfall. Their only exposure to light was the flame from a small fire. They typically woke up about an hour before sunrise. Although light exposure didn’t seem to influence sleep patterns, temperature exposure did. They tended to fall asleep once temperatures began to drop, and to wake up once temperatures started to rise, which leads the researchers to theorize that humans evolved to sleep during the coldest hours in order to conserve energy.

In a New York Times article Dr. Watson, the president of the American Academy of Sleep Medicine, clarifies that although the hunter-gatherers slept for 6 ½ hours, they were in bed for 7-8, a number that matches estimates for Americans.

“Really it’s just the amount that allows people to wake up feeling refreshed and alert,” he added.

Perhaps the main takeaway from this latest study is that sleep quality matters far more than quantity. In America, 20-30% of people have chronic insomnia. Among the indigenous people studied, only 2% showed signs of insomnia. Over 9 million Americans take prescription meds for insomnia, which suggests that our sleep quality isn’t up to par. Whether or not artificial light and digital distraction really do play a role in that still needs further investigation.