If you have lots to do and therefore often skimp on your sleep, then you are probably not a retiree and certainly not a small child. Our sleep duration forms a U-shaped pattern.

When we are young we sleep a lot and when we are old too, according to American research. Americans sleep the shortest when they are 40 years old. Around 50, the number of hours of sleep creeps up again, according to researchers at the Medical College in Georgia. They examined the sleep patterns of 11,279 Americans ages 6 and older who participated in the National Health and Nutrition Examination Survey. This is the first time representative measurements have been made with movement meters. The participants wore a so-called accelerometer 24 hours a day, seven days in a row. While the device doesn’t directly measure sleep time, the amount of exercise does provide an indication of sleep duration, says co-author Dr. Vaughn McCall, expert on insomnia, depression, and suicide.

It is a more objective measure than the self-report on which many sleep studies are based, although the results are quite similar. “We were able to confirm previous findings,” said Dr. Shaoyong Su, who led the study. “People think that children and adolescents sleep longer and they do. In middle age, people sleep less and this also confirms our findings in an objective way.” Sleep time increases when people are past 60.

Pension

With these more objective measurements, the researchers discovered again that, in general, our sleep duration decreases as we age, although they saw a clear U-shape emerge: from the age of 10 people sleep less and less and after the age of 50 it increases again. Japanese and French studies among large groups of people found a similar pattern. The longer sleep duration in people over 60 can simply be explained by the fact that they stop or work less, so that they have to get up less early. But health problems may also explain why older Americans sleep longer, the researchers write.

If we look at sleep efficiency instead of sleep duration, a different picture emerges. Sleep efficiency is the time you actually sleep and not the time you spend sleeping. 85 percent sleep efficiency is considered good. Sleep efficiency also decreased slightly with age, but remained stable between the ages of 30 and 60. Adults therefore sleep just as efficiently, but for a shorter period of time during busy middle age.

“People often think that sleep efficiency goes down directly with age, but we found that there is a stable period, from 30 to 60 years of age, where your sleep efficiency is quite stable,” said Dr. Xiaoling Wang.

Women sleep longer
The researchers also found that women generally sleep longer than men throughout their lives, but tend to go to bed later, especially as they get older. Their sleep is also interrupted more often, especially when they have to take care of the children. On a net basis, they still have about four minutes more sleep per night than men.

A surprising result of the research is that men and women sleep equally efficiently. This is remarkable, because women themselves often report poorer sleep quality and more sleep problems. It is therefore possible that women think that they sleep poorly, while in practice this is not so bad.

Importance of sleep
Finally, the researchers emphasize the importance of sleep. “One thing you can’t overestimate is the impact of sleep,” Wang says. Without enough sleep, “you exhaust your body,” she says. In addition, your ability to adapt to less sleep declines with age.

While sleep deprivation in itself is a risk factor for a host of health problems, from obesity and diabetes to cardiovascular disease, it can also be an indicator of illness, McCall says. He compares the quality of our sleep with the proverbial ‘canary in a coal mine’: sleep complaints can indicate psychological or physical health problems.