Bad Sleep Can Make You Feel Years Older Than You Really Are, Study Suggests

After just two nights of short sleep, a person’s “subjective age,” or how old they feel, can spike by more than four years

A young women asleep in bed
For each bad night of sleep in a one-month period, participants reported feeling three months older, on average, than they really are. Mavocado via Getty Images

Sleep deprivation has been linked with chronic health issues and higher levels of anxiety and depression—it could even make people act more selfish. As a result, the National Sleep Foundation recommends that adults receive at least seven hours of shut-eye each night.

Now, new research offers yet another incentive to prioritize nightly rest: A few nights of fitful sleep can make you feel years older than you really are, according to results from Stockholm University, published last week in the journal Proceedings of the Royal Society B. Consistently good sleep, on the other hand, can have the opposite effect, making you feel younger.

“Sleep has a major impact on how old you feel, and it’s not only your long-term sleep patterns,” Leonie Balter, a psychoneuroimmunologist at the Karolinska Institute in Sweden and a co-author of the study, tells the Guardian’s Ian Sample. “Even when you only sleep less for two nights, that has a real impact on how you feel.”

This feeling is known as “subjective age,” and it describes much more than just a groggy, slow-moving morning. How old a person feels—both mentally and physically—may have a tangible impact on health and lifespan, previous studies have found. Feeling older might reduce energy levels throughout the day and discourage healthy eating, in turn lowering a person’s commitment to exercise and motivation to be social. The age you feel reflects the age you behave, researchers say.

“Age can be understood in multiple dimensions: chronological, biological and subjective,” Chang-Ho Yun, a sleep researcher and neurologist at Seoul National University in South Korea who was not involved in the study, tells CNN’s Sandee LaMotte. “Overall, these findings underscore the importance of adequate sleep in maintaining a youthful subjective age, potentially benefiting both mental and physical health.”

In the first part of their research, Balter and John Axelsson, also a sleep expert at the Karolinska Institute, asked 429 participants ages 18 to 70 a consistent question to gauge their past month of sleep: “On some days you may feel older or younger than your calendar age. What age do you feel right now?”

They found that with each day of bad sleep the average participant had accumulated in the past 30 days, their subjective age increased by nearly three months. And those who experienced no days of bad sleep in the past month said they felt an average of six years younger than their true age.

Next, the duo ran an experiment in which 186 volunteers aged 18 to 46 experienced two consecutive nights of bad sleep—a “sleep restricted” schedule of four hours per night—or two consecutive nights of good sleep—nine hours of “sleep saturation.” Then, each participant described their subjective age.

After two nights of restricted sleep, people reported feeling an average of 4.4 years older than their true age—while those with two nights of saturated sleep felt an average of three months younger.

Scientists found no marked differences in the results between genders, but self-described “early birds” were much more sensitive to the effects of both good and bad sleep—they aged themselves more, on average, than “night owls” did after four hours of sleep, and de-aged themselves the most when receiving a full nine hours of sleep.

The authors write that additional studies might unravel how other factors affect subjective age, such as the timing or quality of sleep.

“Another important thing to consider in future research is an exploration of these mechanisms over time,” Serena Sabatini, a psychologist at the University of Surrey in England who was not involved in the study, tells the Guardian. “This study tells us that a bad night of sleep can impact how we feel the day after, but what are the cumulative effects of bad sleep for months and years?”

In an unrelated study published last week, in the journal BMJ Open, researchers monitored participants’ sleep over a ten-year period. They found that consistently active people also received, on average, healthier amounts of sleep.

“If you protect your sleep, you can feel younger,” Balter tells New Scientist’s Chen Ly. “We know those who feel younger than their actual age live healthier and longer.”

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