STOCKHOLM, March 28 — It’s often said that age is all in the mind. But a study in Sweden shows that feeling young is not just a matter of subjective perception. It’s also a question of sleep.

You may have looked at yourself in the mirror and felt as if you didn’t "look your age.” This is because we don’t always have a clear idea of our biological age. American researchers have previously discovered that, from the age of 30 onwards, most people tend to underestimate their age. In other words, they think they’re younger than they really are.

While this discrepancy between subjective age and biological age may sound trivial, it can actually have serious medical consequences. Indeed, the illusion of youth is associated with better cognitive performance, greater life satisfaction and, more generally, better physical and mental health.

So what can we do to help us feel young? Is it enough to dress or talk like a young person to subconsciously become one? According to researchers at Stockholm University, the secret could lie in the quality of your sleep. "Given that sleep is essential for brain function and overall well-being, we decided to test whether sleep holds any secrets to preserving a youthful sense of age,” says Leonie Balter, researcher at the Department of Psychology, Stockholm University, quoted in a press release.

Sleep well to feel young

To do this, Leonie Balter and colleagues first questioned 429 individuals aged between 18 and 70 about how they felt about their age. They also asked them to estimate the number of nights they had not slept enough in the month preceding the study, as well as their level of sleepiness. It turned out that, for every night of insufficient sleep, the volunteers felt on average 0.23 years older.

In a second phase, the academics conducted an experiment with 186 participants aged between 18 and 46. They asked them to sleep for just four hours for two nights, and then to have two full nights of sleep (with nine hours of sleep each time). It turned out that the volunteers felt on average 4.4 times older when they didn’t get enough sleep.

The research team hypothesised that the effects of sleep on perceived age were linked to the level of sleepiness people felt. They found that feeling alert made people feel four years younger than their biological age. Conversely, extreme sleepiness contributed to subjective aging. Subjects who struggled to stay awake felt six years older.

These findings, published in the journal Proceedings of the Royal Society B, show the extent to which the quality of our sleep can benefit or, on the contrary, undermine our mental health. "Safeguarding our sleep is crucial for maintaining a youthful feeling. This, in turn, may promote a more active lifestyle and encourage behaviors that promote health, as both feeling young and alert are important for our motivation to be active,” explains Leonie Balter. — ETX Studio