Sleep Study Has Warning for Night Owls

"If you want to feel young, the most important thing is to protect your sleep." So says the author of a new study suggesting that just two consecutive nights of poor sleep make a person feel years older than they really are. Researchers in Sweden surveyed 429 people aged 18 to 70 about how old they felt, their sleepiness, and how many nights they had slept poorly in the previous month. They found that for every night of poor sleep reported, participants felt three months older than their true age on average, per the Guardian. In contrast, those who reported no poor nights of sleep felt nearly six years younger on average.

In a second survey, researchers polled 186 volunteers aged 18 to 46 on how old they felt after sleeping only four hours for each of two consecutive nights and after staying in bed for nine hours for each of two consecutive nights. With ample sleep, the participants reported feeling three months younger than their true age on average, per the Guardian. But comparing the experiences, participants reported feeling an average of 4.44 years older than their true age when sleep was limited. Some felt more than a decade older. Morning people, used to waking and going to bed early, were particularly affected by the limited sleep. But evening people "typically felt older than their true age even after plenty of sleep," the Guardian reports.

This is important. In this study, feeling older coincided with more sleepiness. But previous research has linked higher subjective age to depression, per New Scientist. "We know those who feel younger than their actual age live healthier and longer," Dr. Leonie Balter, a psychoneuroimmunologist at Stockholm's Karolinska Institute and lead author of the study published Wednesday in Proceedings of the Royal Society B, tells the outlet. But subjective age is "malleable," Balter adds, per the Guardian. "If we can make people feel younger, they may be able to have the associated benefits, such as being more willing to take on new experiences and being socially active and physically active." (More sleep stories.)