While getting older is a universal phenomenon, aging is more complicated than it appears.
There is your chronological age — the literal number of years you’ve been alive. There’s also your biological age, which refers to how old your body’s cells appear — a measure based on biological markers.
Then there is your subjective age. This is how old you feel.
While your feelings might seem a less reliable measure than the number of birthday candles on your cake, subjective age is an important predictor of later-life health outcomes. Studies suggest people who feel younger than they actually are tend to have healthier brains, a greater sense of well-being, and live longer.
While studying how people perceive age-related changes, University of Exeter post-doctoral research associate Serena Sabatini noticed something else: Subjective age can be influenced by how well people sleep.
Sabatini and colleagues later found sleep quality is related to self-perceptions of aging. Their research was published in October in the journal Behavioral Sleep Medicine. The study found that people who said they had bad sleep felt older — and viewed aging more negatively.
“We found that the more people feel younger than their age, the better is their quality of sleep,” Sabatini tells me.
“People who perceive aging more negatively think that losses are an inevitable part of aging and that they have no power to control the way they age,” she adds.
But scientists argue people have more control over healthy aging than they likely realize.
How the discovery was made — Sabatini’s work is part of the PROTECT study, which is an effort to understand what helps people stay cognitively healthy when they are older. Her team surveyed 4,482 people over the age of 50 and asked them what age they felt they were.
They then calculated the discrepancy between their perceived age and chronological age, dividing the participants into those who feel older than their age, feel younger, and those who feel their actual age.
Participants were also asked if they’ve experienced negative and positive age-related changes in regards to their physical health, mental health, social relations, cognition, and lifestyle. They were asked if they agreed with statements like “with my increasing age, I realize I have less energy” and “with my increasing age, I realize that my memory is declining.” They were asked these questions twice, separated by a year.
Overall they found people who slept poorly also feel older and have a more negative view of aging. Perceived alertness after waking up was the sleep factor with the strongest association with feeling bad about aging.
However, “we do not know whether being negative about aging is a consequence of having poor sleep or whether having poor sleep is a consequence of being negative about aging,” Sabatini explains.
“To understand this, we need to follow participants over time,” she says. “This is important because, for instance, if we understand that poor sleep leads to negative perceptions of aging, by implementing intervention programs that solve sleep problems we can also promote better perceptions of aging.”
Why subjective age matters
While more research is needed to understand this association more fully there are a few ideas that make a lot of sense if you’ve ever tossed and turned for a night: It’s possible, the study states, that people may feel older and more negative about feeling older because bad sleep results in a bad mood. It’s hard to feel good about your body if you’re groggy and ache.
But this also lends itself to opportunity: Sleep becomes an opportunity for intervention.
Sabatini hopes her research can inform the development of future intervention programs “that aim to promote better perceptions of aging and/or better quality of sleep in older age.” If you can help people sleep better, it’s possible you will also help them process getting older. Sabatini would like to pursue this idea in the future and test whether or not people who are more negative about aging are objectively experiencing poorer sleep, through tests like polysomnography.
Because what’s at stake is more than being cranky: Subjective age influences overall health and longevity. People who feel negative about aging are less likely to engage in healthy behaviors like eating well, exercising, and socializing, Sabatini explains. Conversely, those who perceive aging and their own aging more positively are more likely to feel in control of their futures — and take the steps to live well.
People who are positive about aging are also less likely to experience stress and low mood. “This, together with the accumulated benefit of engaging in healthy behaviors, increases the likelihood of these people maintaining better health in older age,” Sabatini says. Subjective age, she says, “is a great example of how the mind and body interact.”