Did you know that not getting enough sleep can make you feel older than you actually are? A new study has shown that feeling sleepy can make you feel up to a decade older, and just two nights of insufficient sleep can add more than four years to this perceived aging.

In a two-part study published in the scientific journal Proceedings of the Royal Society B, researchers at Stockholm University investigated the link between the way a person perceives their age and their 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. Age is more than just a perception. We know those who feel younger than their actual age live healthier and longer," said Leonie Balter, a researcher at the Department of Psychology, Stockholm University.

In the first part of the study, the team evaluated 429 individuals between the ages of 18 and 70. The participants were asked about their subjective age perception, the frequency of insufficient sleep days in the preceding month, and their level of sleepiness. The results revealed that for every night of inadequate sleep reported in the past month, participants felt an average of 0.23 years older.

In the second part, the researchers conducted an experimental sleep restriction study to ascertain whether sleep deficiency was directly causing the participants to feel older. The trial involved 186 individuals between the ages of 18 to 46. Their sleep was restricted for two nights to just four hours each night. At a later time, the same participants were allowed to sleep sufficiently for two nights, with a total of nine hours in bed each night.

The results showed that participants felt on average 4.4 years older after sleep deprivation compared to when they sufficiently slept.

"The effects of sleep on subjective age appeared to be related to how sleepy they felt. Feeling extremely alert was related to feeling 4 years younger than one's actual age, while extreme sleepiness was related to feeling 6 years older than one's actual age," the news release stated.

"This means that going from feeling alert to sleepy added a striking 10 years to how old one felt. 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," Balter said.