Lifespan or Healthspan? A New Chapter in Aging Research
Aging has been a subject of intense fascination for centuries. Scientists, philosophers, writers, anthropologists, sociologists, explorers and laypersons have discussed, written about, speculated about, and searched for the keys to the aging process, in hopes of discovering the elusive fountain of youth.
For the last several decades, in particular, scientists in the field of gerontology have directed their attention towards identifying aging factors that, if modified, could decelerate or even halt aging. For example, modern aging researchers in the field of genetics have uncovered two genes—APOE and FOXO3A—that have been shown to be significantly involved in the aging process.
Biological researchers are currently investigating the potential role of certain rare alleles in extending longevity. Other researchers have identified age-related proteins known as sirtuins. Sirtuins control several biological pathways and are present in antioxidants such as resveratrol, which is the primary ingredient in red wine.
And so on, with more research taking place every day at Universities and other research facilities around the world. The facts of aging—what is happening on a biochemical, genetic, and physiological level—remain rich for exploration.
There are still basic questions that remain unanswered. For example, what triggers aging in our tissues and cells? Why do these triggers occur? And, what are the specific biological processes impacting aging at the cellular and molecular levels? However, significant progress has been made in the last decade with more to be expected on the horizon.
So far so good. But how does this relate to good health?
Not as much as one would think.
When it comes to aging research, lifespan has been the most common measurement, mostly because it is objective and easy to measure. As such, scientists have focused on prolonging lifespan based on the assumption that lifespan was a good indicator of the number of years of good health. Recent experiments, however, have suggested that this is not necessarily the case.
In 2015, a team of researchers at the University of Massachusetts Medical School, in an anti-aging study involving tapeworms, divided lifespan into what they called healthspan and gerospan.
The team defined healthspan as the number of years a body functions at 50% or better capacity, with gerospan being the number of years from that point until the body’s eventual death. The team’s going-in assumption was that a healthy long-lived organism would have an extended healthspan and compressed gerospan. What they found, however, was that lifespan and healthspan were not correlated.
In fact, their research showed that the long-lived organisms spent a higher percentage of their extended lifespan in an unhealthy, frail state. They concluded that aging research must include additional factors beyond lifespan alone.
As lead researcher, Tissenbaum concluded, “Ultimately, all medical research is aimed at prolonging life – but we must strive to prolong healthy life. Therefore, our challenge remains defining health and the ability to test and quantify healthy living.” Moving forward, this particular research team has decided to turn towards identifying genes and interventions that extend healthspan and lifespan.
Another challenge to the “lifespan as an indicator of healthspan” assumption arose from recent experiments, particularly in mice, which have demonstrated that significant improvements in health do not necessarily result in increased lifespan. For example, NIA researchers examining the effects of resveratrol in mice on a normal diet found that resveratrol had an extremely positive impact on health, but did not increase lifespan.
It follows that life expectancy can no longer be considered as the best indicator of good health.
Let’s talk about healthspan.
Understanding how to extend healthspan apart from its impact on life expectancy has become a growing focus of new research, and for good reason. Few of us would look forward to the prospect of living to be 100 if we knew that a good number of those extra years would be spent in a state of considerable and progressive physical and/or mental decline.
Thus, while there is still a place for lifespan research, healthspan research focused on the postponement and prevention of chronic disease and disability has tremendous potential to allow us to live healthier longer.
The Alliance for Aging Research in Washington, DC has reported that eighty percent of Americans 65 and older have at least one chronic condition, such as cancer, pulmonary disease, kidney disease, cardiovascular disease, arthritis, diabetes, and neurological diseases such as Alzheimer’s and Parkinson’s. Fifty percent have two or more.
That means most elderly Americans are battling serious illnesses and disabilities throughout their senior years. According to Alliance president and CEO, Susan Peschin, “One hundred years ago we didn’t have the luxury of old age. While we have been able to add years to life, we have not been able to maintain health and vigor. The idea is to compress morbidity and lengthen the period of healthy and vigorous life.”
The average American lifespan is 79 years. The average American healthspan–the number of years without chronic disease–is 64 years. (The longest confirmed lifespan is 122.5 years, but we’ll come back to that later.)
This means that the average American will spend the last fifteen years of his or her adult life suffering from one or more chronic diseases. The following graph shows how this can play out under various scenarios.
This graph is intended to illustrate why understanding how to extend healthspan apart from its impact on life expectancy is a growing focus of many studies. Clearly, the worst case scenario is that third one, living to be 100 years old but sick for the last thirty-five years. The ideal scenario is the one showing extended life and health span, which is hopefully where modern research is taking us.
So let’s get back to that person who lived to be 122.
The holder of the longest confirmed human lifespan was Jeanne Louise Calment a French woman who lived for 122 years and 164 days. She spent her entire life in Arles, France, outliving both her daughter and grandson by several decades.
Calment was, by all published accounts, a remarkable lady. When she was 85 she took up the sport of fencing. She rode her bicycle up until age 100. Calment lived alone until just before she turned 110 when she moved into a nursing home due to vision complications.
Even still, she remained in good shape and continued walking until age 114, when she suffered a bone fracture necessitating surgery. After the operation, Calment began using a wheelchair. At age 119 she reportedly weighed approximately 99 pounds. She died three years after that.
Remember that ideal lifespan/healthspan scenario above? Extend that healthspan period for another 22 years, and that is Calment. According to her, the secret to good health and longevity is a diet rich in olive oil, port wine and the consumption of 2.2 pounds of chocolate per week. She is said to have remained mentally intact until her very end.
Unfortunately, we can’t all live as long as, or as healthily as, Jeanne Calment. At least not yet.
While advancements in medicine and technology may have resulted in an increased overall lifespan, a widespread adherence to exercise, dieting, and other healthy lifestyle elements may be necessary to obtain a comparable increase in healthspan.
Thus, while lifespan research remains an important area of study, healthspan research holds promise for revealing ways to delay or prevent disease and disability so that many of us can live healthier longer. And, with that, we may have the opportunity to enjoy our later years by partaking in more of life’s experiences, spending time with friends and family, doing things that make us happy, and simply savoring everything in life that makes it worth living.