Biology of Aging
Living long and well: Can we do both? Are they the same?
You can hardly turn on your computer these days without being bombarded with advertisements that pop up trying to convince you of the power of a pill that will make you live longer or a cream that will help to revive your youthful vigor and appearance. The search for ways to stop or reverse the aging process is a near-obsession in popular culture. The likelihood of discovering a scientifically proven “anti-aging” elixir is slim, but researchers believe their work will reveal ways to improve a person’s ability to live a longer, healthier life. They express these goals in terms of “lifespan” and “health span,” respectively.
Lifespan is the length of life for an organism. For instance, if you live to age 99, that would be your lifespan. Maximal lifespan is the maximum number of years of life observed in a specific population. It differs from species to species. The maximum recorded lifespan for humans, reported in 2010, was 122.5 years for females and 116 years for males.
Lifespan is a common measurement in aging research. That’s because it is clear-cut and easy to measure—an organism is either alive or dead. Scientists look for factors such as genes, environment, and behavioral traits (including diet) that may contribute to an organism’s lifespan. Altering a factor to see if it changes lifespan can provide evidence about whether or not that specific factor is important for aging. For instance, when researchers suspect that a specific gene has an effect on lifespan, they may test their hypothesis by modifying the activity of that gene (perhaps lower its activity by deleting the gene or increase its activity by adding an extra copy of it). If the life of the animal with the modified gene activity is longer or shorter, then the gene probably does play a role in lifespan.
Researchers are finding that lifespan may be influenced by external factors, as well. This has been demonstrated in animal studies. NIA’s Interventions Testing Program (ITP) examines a variety of compounds for their effects on the lifespan of mice. Compounds studied include dietary supplements, hormones, and anti-inflammatory drugs. In one ITP study, male mice treated with aspirin, an anti-inflammatory drug, displayed a moderately increased lifespan. In another ITP study, masoprocol, an anti-inflammatory drug that has antioxidant properties, was found to increase longevity of male, but not female, mice. These and other findings may help scientists identify compounds to test in humans for their effects on aging. While some of the compounds tested in the ITP already have a clinical use for humans, scientists are clear: These compounds should be used only as prescribed and not for lifespan extension at this time.
The ability to withstand disease could also be central to lifespan. Studies of exceptionally long-lived people are helping to establish patterns of health decline and increased disease (called morbidity) with old age. For example, do health problems start around the same age in all people and expand over extra years of life for the long-lived, or are the problems delayed, occurring closer to the end of life among exceptional agers? Evidence from a Danish longitudinal study of 92- to 100-year-olds found that health problems seem to be delayed, appearing closer to the end of life. This is not a certain outcome, but in many studies, the average centenarian seems to be in better health than the average 80-year-old. However, living to 100 does not mean never having any health issues. In the New England Centenarian Study, researchers have developed three categories for their long-lived participants. They are characterized as “survivors,” “delayers,” or “escapers,” depending on whether they have survived a life-threatening disease, delayed a serious health problem until much later in life, and/or escaped any serious health events.
Scientists used to think that long life was a good indicator of health span, or years of good health and function. However, some experiments, particularly in mice, demonstrate significant improvements in health, without actually increasing lifespan. For example, NIA scientists and grantees (that is, scientists at a university or other institution whose research is funded by NIA) examining the effects of the wine-derived compound resveratrol in mice on a normal diet found the compound positively influenced the health of the mice—resveratrol-treated mice had better bone health, heart function, strength, vision, coordination, and cholesterol than the control group. But, resveratrol did not increase lifespan. (Lifespan was increased, however, in mice on a high-fat diet supplemented with resveratrol.)
Understanding how to extend health span—apart from its impact on longevity—is a growing focus of many studies, and for good reason. Imagine a society where a majority of people live to be 100, but along with the added years comes considerably more physical decline. While there is still a place for lifespan research, health span research holds promise for revealing ways to delay or prevent disease and disability so that we can live healthier longer.
Uncovering Family Secrets to a Long LifeMost of what we know about factors that can contribute to a long lifespan and health span is based on research in animal models. However, NIA-funded research like the Long Life Family Study is taking what we’ve learned in animals and seeing if it applies to human aging. This study is collecting data from families with at least two siblings who have lived to a very old age in relatively good health. Along with asking questions about their family and health history, the researchers conduct physical assessments and health screenings and collect a small blood sample for genetic tests. What researchers learn about common characteristics shared by these families could one day be used to guide lifestyle advice and medical treatments.
Publication Date: November 2011
Page Last Updated: January 18, 2012