Sleep deprivation could make you feel several years older than you really are.
How old someone feels, or their subjective age, has been associated with various physical and mental health outcomes, particularly depression. “Age is more than just the perception,” says Leonie Balter at the Karolinska Institute in Sweden. “We know those who feel younger than their actual age live healthier and longer.”
Given sleep’s importance for our mental and physical health, Balter and John Axelsson, also at the Karolinska Institute, decided to investigate if it affects our subjective age.
The pair enlisted 429 people – aged 18 to 70 years old – to take a survey on how old they felt and how much they had slept in the past 30 days.
They found that reporting insufficient sleep was linked to the participants feeling older than they were, with each day of poor sleep adding an average of 0.23 years to their subjective age. In contrast, those who reported getting sufficient sleep throughout the 30 days had a subjective age that was 5.81 years younger on average than their real age.
In the second part of the study, the pair recruited 186 more people. Over two weeks, these participants were asked to aim for 9 hours of sleep across two consecutive nights, recorded via a sleep log and sleep-tracking wrist device. They were then told to restrict their sleep to just 4 hours for two consecutive nights.
After this period of sleep restriction, they reported feeling an average of 4.44 years older than they were, while under the 9-hour sleep condition, they felt 0.24 years younger. Compared with those who felt the least fatigued, those who were the most tired reported feeling around 10 years older.
The findings show that sleep is a key indicator of how old some people might feel, which has been linked to our health, says Balter. “If you protect your sleep, you can feel younger,” she says.