You are what you sleep: Study shows how young you feel depends on how much sleep you get

You don’t feel like yourself if you don’t get enough sleep, but researchers at Stockholm University say losing out on those Zs actually makes you feel older than you really are.

At issue is “subjective age” — the age we “feel” — rather than how many times we’ve been around the sun. Researchers discovered that for every day a test subject slept poorly, they felt .23 years older than their actual age, on average. For those who reported feeling the least awake on a scale of one to nine, they felt as many as 10 years older than they actually were. 

The study also used sleep restriction to confirm sleep survey results. After being restricted to 4 hours of sleep for two nights in a row, the subjects, regardless of their actual age, felt 4.44 years older than the group that got 9 hours of sleep for two nights straight.

“Sleep and sleepiness play a profound role in shaping our sense of age,” the researchers concluded. “The findings revealed that insufficient sleep and sleepiness led people to feel older than their actual age and support that a good night’s sleep is central for feeling younger than one’s actual age.”

Also, the researchers say the older the test subjects were, the more pronounced the “aging” effect was.