It is one of the most common tips for a good night’s sleep: sleep at least eight hours a night. But a professor at Harvard University claims that eight is not the magic number.
Dr. Daniel Lieberman, of the university’s Department of Human Evolutionary Biology, said that “people actually do better when they get seven hours of sleep.”
“The idea that you need eight hours of sleep has been around for a long time, actually since the industrial revolution,” he said in an episode of the Diary of a CEO podcast last week.
Dr. Lieberman used populations that have no produced light as an example – electricity, telephones, televisions. Research has shown that those who don’t spend all day on their phones or staring at screens need less sleep.
Dr. Harvard University professor Daniel Lieberman said most people should aim for seven hours of sleep a night instead of eight.
The seven-hour rule falls on the lower end of the Centers for Disease Control and Prevention’s (CDC) recommendations, though recent research supports Dr. Lieberman supports
“Colleagues in my field — in evolutionary medicine — have placed sensors on people who don’t have all the things we’re told destroy sleep. We’re told that TV and lights and our phones and all these things keep us from sleeping,” he said.
“If you put sensors on people who don’t have electricity and they don’t have TVs and no phones and none of these gadgets, it turns out they sleep six or seven hours a night, and they don’t nap.”
So this idea that natural people sleep eight hours a night is just nonsense. It’s just not true.’
By limiting screen time, you may need less sleep in the long run, he said.
The recommendation is at the bottom of guidelines from the Centers for Disease Control and Prevention (CDC), which states that all Americans should get seven to nine hours of sleep every night.
Children ages six to 12 need nine to 12 hours a night, while teens should get eight to 10 hours, the agency said.
However, a growing body of research supports Dr. Lieberman’s theory.
A study published last year in the journal Nature aging found that seven hours is the ideal amount for middle-aged and older adults.
The research suggested that anything more or less than that amount was associated with cognitive problems, such as the inability to remember, learn new things, focus, solve problems and make decisions.
In addition, those who did not get seven hours were more likely to have symptoms of depression and anxiety.
“People actually do better when they sleep for seven hours, and yet we’re told that if you don’t sleep for eight hours, something is wrong,” Dr. Lieberman said.
According to CDC figures, one-third of Americans ages 18 to 64 don’t get enough sleep — at least seven hours a night.
This drops to 26 percent as adults are over age 65, but that’s still more than a quarter of adults who don’t get enough sleep.
A lack of sleep is consistently linked to chronic health problems such as heart disease, kidney disease, high blood pressure, diabetes, stroke, obesity and depression.
However, there are a few caveats to the seven o’clock rule.
“People who are sick may sleep more, so there are some biases that creep into how you analyze the data, but it turns out that seven — for most people — is optimal,” said Dr. Lieberman.
Certain populations are also more likely to have varying sleep schedules. While a teen may sleep in on weekends, older adults may get less rest or have more interrupted sleep.
For a good night’s sleep, the American Academy of Sleep Medicine recommends going to bed at the same time every night and waking up at the same time every morning, including weekends.