Are you a rapid ager? Biological age is a better health indicator than the number of years you've lived, but it's tricky to measure

Do you ever wake up some days and think, “When I was younger, I could survive on just four hours of sleep, but now it seems like I need 10”? Or have you ever walked out of the gym and “felt” your knees?

Almost everyone experiences these kinds of signs of aging. But there are some people who seem to defy their age. The late U.S. Supreme Court Justice Ruth Bader Ginsberg stayed on the bench until her death at age 87. The “Great British Bake Off” judge Mary Berry, now in her 80s, continues to inspire people all over the world to bake and enjoy life. And actor Paul Rudd was named People magazine’s “Sexiest Man Alive” in 2021 at age 52 while still looking like he’s in his 30s. Is age just a number then?

Researchers have focused a lot of attention on understanding the causes and risk factors of age-related diseases like Alzheimer’s, dementia, osteoporosis and cancer. But many ignore the major risk factor for all of these diseases: aging itself. More than any individual risk factor such as smoking or lack of exercise, the number of years you’ve lived predicts onset of disease. Indeed, aging increases the risk of multiple chronic diseases by up to a thousandfold.

However, no two people age the same. Although age is the principal risk factor for several chronic diseases, it is an unreliable indicator of how quickly your body will decline or how susceptible you are to age-related disease. This is because there is a difference between your chronological age, or the number of years you’ve been alive, and your biological age – your physical and functional ability.

As the author notes in her TED Talk, aging is not just a number.

I am a scientist interested in redefining “age.” Instead of benchmarking chronological age, my lab is invested in measuring biological age. Biological age is a more accurate measure of healthspan, or years lived in good health, than chronological age, and doesn’t directly correlate with wrinkles and gray hairs. Rapid agers experience a faster rate of functional deterioration relative to their chronological age.

My grandmother, who lived to be 83 but was bedridden and could not remember who I was for the last few years of her life, was a rapid ager. My grandfather, on the other hand, also lived until he was 83, but he was active, functional and even did my homework with me until he passed away – he was a healthy ager.

With the unprecedented growth of the world’s aging population, I believe that figuring out ways to measure biological age and how to maintain or delay its advance is critical not only for individual health, but also for the social, political and economic health of our society. Detecting rapid agers early on presents an opportunity to delay, change or even reverse the trajectory of biological aging.