Reviewed by Michael W. Smith, MD on September 20, 2018
From the WebMD Archives

Laura Bridges celebrated her 100th birthday this month. The year she was born in rural Oglethorpe County, GA, the flu killed an estimated 50 million people worldwide. As a result, U.S. life expectancy that year was just 36 years for a man and 42 for a woman. The following year, life expectancy rose back up to the more typical 55.

These days, while statistical life expectancy in the U.S. is about 80 years, living well into one’s 80s or 90s is a perfectly realistic expectation for many. Even centenarians -- people who are 100 years old or more -- are on the rise. In 2015, some 72,000 Americans were centenarians. That’s a whopping 43% increase from just 50,000 in 2000.

As centenarians’ numbers grow, researchers want to know what separates them from those who live the average, expected 80 years. Of course, you can’t underestimate the value of exercise, a good diet, and other healthy choices. But studies show genes are pretty important, too. So do you have to win the genetic lottery to live a whole century? Or can science unlock the secret to spreading the genetic wealth?

The Case for Genes

Asked if she expected to live a hundred years, Bridges says, “Sure! I take after my grandmother.” Bridges has in fact outlived her grandmother, who lived to be 99. Her sister Virginia lived to 99 as well. Another sister, Dot, is 90.

Longevity runs in families, which has led scientists to search for the genes that might give some a chronological edge.

“Several genes have been identified,” says Sofiya Milman, MD, director of human longevity studies at Albert Einstein College of Medicine in Bronx, NY. “Most [long-lived people in our research] have a few of these genes, but not all of them. And there are probably many more genes we can discover.”

Longevity researchers like Milman aren’t just studying people who live to a very old age, but people who age very well. After all, if you want to live to an exceptionally old age, you’re probably interested in more than just extra years. You want to enjoy those extra years with a sharp mind and good physical health.

The SuperAging Study, an ongoing clinical trial at Northwestern University, includes people who are older than 80 but still have the memory of someone in their 50s. It’s not such a tall order. Exceptionally old age and exceptionally good health for that age, both in body and brain, seem to go hand in hand. “We think they might be on a different trajectory of aging,” says Emily Rogalski, PhD, who leads the SuperAging Study.

The trial compares super-agers’ brains to the brains of average-agers -- people whose overall health and memory align with their age. Super agers’ brains, the study has found, look more like the brains of 50-year-olds than like the brains of 80-year-old average-agers.

Other studies support the idea of a slower biological clock as well. In a study that compared older adults ages 95 to 112 with much-younger older adults, many of the exceptionally long-lived people developed age-related illnesses, such as cancer, heart disease, diabetes, osteoporosis and stroke, up to 24 years after the average age for developing these conditions.

“They don’t just live longer, they live healthier, and maybe that’s why they live longer,” Milman says. A follow-up to this study found that children of long-lived people tend to have lower rates of age-related diseases, too.

Bridges has enjoyed a disease-free life herself. She lived independently in the home she purchased with her husband, Joseph “Joe” Bridges, in the Atlanta suburb Doraville in 1962 until she was 98. When she began to show signs of dementia at 98, some 20 years after the average age it develops, her son moved her to an assisted living facility.

Researchers have begun to identify genes that might contribute to the slower aging Bridges and others like her enjoy. In some cases, the gene’s function explains why it might extend life. For example, one gene variant common in exceptionally long-lived people is connected to higher levels of good cholesterol (HDL) and lower risk for dementia and Alzheimer’s. Another, also connected with higher HDL, seems to come with better overall health of the arteries. A couple of other genes associated with longevity appear to regulate inflammation and oxidative stress, a type of cumulative damage to the cells. Both are precursors to many age-related chronic diseases. Researchers have found other genes that seem to be common in centenarians or other long-lived people, though they don’t know what those genes do.


The Case for Lifestyle

Of course, genes don’t explain everything. They don’t tell scientists why life span, and the number of centenarians, has increased so much in the last 100 years.

“We’ve extended life expectancy almost a third of a century [in that time], and that’s mostly from environment,” says Claudia Kawas, MD, who co-leads The 90+ Study at University of California Irvine. The study explores aging well and dementia in people 90 years old and up.

Kawas notes that improvements in public health, such as reduced pollution, discovery of antibiotics, development of vaccines, i

mprovement in education, and lifestyle changes have all added to life expectancy. In the last 20 years, aggressive treatment of high blood pressure and high cholesterol have helped, too.

Thomas Frieden, MD, MPH, former director of the CDC, credits public health advancements with 25 of the 30 years that lifespan has increased in the U.S. in the last century. It’s due to ongoing scientific, medical, and public health advancements, and lifespan is expected to increase. Half the children born in the U.S. in 2000 could live to be 103 years old, projections say. Genes may account for only a quarter to a third of human lifespan. When you choose a lifestyle that promotes longevity, you could reap many of the same benefits as those who hit the genetic jackpot at birth.

Keeping up with your friends seems to contribute to aging well, too. Bridges has held on to the same two gal pals since 1962. “I’ve got Eleanor and I’ve got Betty,” she says. The three moved to the same street in Doraville within a month of one another in 1962, saw each other through the deaths of their husbands, all within in the same 6 months, and continued to visit as often as they could until Betty passed away last year.

The super-agers in the Northwestern University study say that they have more satisfying, high-quality relationships than their average-ager peers. They are more likely to say they have friends they can trust and who share their interests.

“When you’re staying in touch with your friends, deciding to go out to lunch rather than stay at home, maybe in addition to making you feel good, that’s doing something good for your brain, too,” Rogalski says.

Maybe all of these things -- a healthy lifestyle, rewarding relationships -- make a person happy. Or maybe happy people seek out these things. Either way, happiness seems to be a predictor of longevity. In a study that followed more than 31,000 adults for 24 years, those who rated themselves “very happy” were less likely to die during the study than those who called themselves “pretty happy” or “not happy.”

Asked for her secrets to a long, healthy life, Bridges offers with a shrug that maybe it’s the vegetables she’s eaten a lot of. She’s exercised from time to time, she adds, never smoked or drank, and she’s worked hard. “And I’m happy,” she adds. “I’ve always been happy.”

Leveling the Genetic Playing Field

Bridges, like many others her age, may simply have a genetic edge over others in the race to live the longest -- and the best. “I don’t know why I’m living so long,” she laughs. “I can’t figure that one out.” Those who aren’t so lucky will have to pick up the slack with plenty of leafy greens and exercise, and a life that’s heavy on friends and free of tobacco.

But one day, what scientists learn now from the genetically lucky could give everyone a boost. If aging at a slower pace protects the exceptionally old from many diseases at once, how can science slow the ticking of average-agers’ clocks, too?

Currently, scientists attack age-related, chronic diseases in the same way they attacked contagious illnesses 100 years ago: one by one. That worked for contagious conditions, but that’s not the right approach for heart disease, diabetes, and other chronic conditions, says Jay Olshansky, PhD, a professor of public health at the University of Illinois at Chicago, where he studies centenarians. “When you reduced infectious diseases, you got decades of life in return, but we only get marginal improvements in longevity when we make [improvements in] the major diseases that kill us today.”

That’s because when you reduce the risk of death from one age-related disease, something else takes its place. “If you cure cancer or heart disease,” Olshansky says, “you’re going to get more people with Alzheimer’s disease.”

The solution? Slow the aging process to reduce risk of all age-related diseases rather than just one. In much the same way that many new cancer therapies target the gene that causes the cancer, new drugs could one day switch certain genes on or off to help average-agers live longer, disease-free lives.

Current research explores the possibility for targeted therapies, as well as other drugs, to slow the aging process. One good candidate is metformin, a safe, cheap medication for type 2 diabetes that’s been in use for more than 50 years. Studies suggest that it delays aging in animals. The TAME (Targeting Aging with Metformin) trial, expected to launch late this year or early next year, will be the first clinical trial to test the hypothesis in people.

“A minor intervention that slows aging would be bigger than a cure for cancer,” says Olshansky, “because it would influence more than just cancer. It would influence heart disease, stroke, Alzheimer’s, osteoporosis, everything that goes wrong with us. If we could slow aging, our world would change in very positive ways.”

Show Sources

Laura Bridges, centenarian.

Sofiya Milman, MD, director of human longevity studies, Albert Einstein College of Medicine, New York.

Emily Rogalski, PhD, associate professor of psychiatry and behavioral sciences, Northwestern University Feinberg School of Medicine, Chicago.

Claudia Kawas, MD, professor of neurology and of neurobiology and behavior, University of California, Irvine.

Jay Olshansky, PhD, professor of public health, University of Illinois at Chicago.

Thomas Frieden, MD, MPH, former director of the CDC.

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