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    Ideas | Bernhard Warner

    Why women live longer than men — and how men will benefit from it

    Why women live longer than men — and how men will benefit from it.
    Hanna Barczyk for The Boston Globe

    Whenever he speaks on the science of aging at a medical conference, Dr. Thomas Perls, a geriatrician and researcher, likes to kick things off with a brief quiz. Do you deal well with stress? he asks the audience. If so, add five years to your life. Do you smoke? If yes, subtract 15 years. As the questions continue — about exercise, diet and the longevity of family members — you can see people squirming in their seats or beaming with relief as they make the mental calculations to determine how long they can reasonably expect to live. At the start of this life expectancy quiz, Perls tells the men to begin at a baseline of 86 years before adding and subtracting years. For the women, it’s 89 years. Why spot the women additional years?

    “Women are stronger when it comes to aging,” says Perls, the director of the New England Centenarian Study at Boston Medical Center. “They’re just much better at it.”

    We’ve known this for ages, but never quite appreciated how truly rare it is. “Humans are the only species in which one sex is known to have a ubiquitous survival advantage,” says Dr. Stephen N. Austad, director of the Nathan Shock Center of Excellence in the Basic Biology of Aging at the University of Alabama at Birmingham. Science still cannot definitively tell us why women live longer because until recently this gender advantage had been largely overlooked, or outright ignored — mansplained away as no big deal, you might say. It’s an area of research, Austad says ruefully, “that’s little studied.”

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    But that’s beginning to change. Understanding the complex biology for why women are better built to withstand life-threatening illnesses, and last longer, could revolutionize how we treat the diseases of old age, and ultimately prolong the lives of both sexes. “This gap,” Austad says, “it’s not going away. That’s the key thing. There’s real underlying biology here, and I think we ignore that at our peril.”

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    The social factors that contribute to increased longevity are beyond dispute. Study after study, as well as Perl’s quiz, shows that a low-stress lifestyle, free of smoking and excessive alcohol, combined with a healthy diet and exercise, will add years to our lives. Public health campaigns to get men across the industrialized world to improve their diets, lose weight, quit smoking, lay off the booze and engage in less risky activities have led to a narrowing of the gender longevity gap here and there. This advice is meant to be sexist. Act more like a sensible female, and less like a shortsighted male, and you’ll live longer. But that thinking only goes so far. There are genetic and biological factors at play that deal you a better hand for living longer. And women, far more often than men, hold these cards.

    And they do so despite considerably longer odds. Women suffer from higher levels of stress, depression and anxiety, and are far more likely to live in poverty. And yet females in the United States outlive men by five years — 81.1 to 76.1 years. In my adopted country, Italy, statistics point to my wife living to 85, roughly 4.5 years longer than Italian males.

    The disparity is so consistent — the female-male mortality rate holds reliably true within income bracket, education level, and geography — that medical researchers have a name for this phenomenon: the female survival advantage. It’s true nearly everywhere on earth, and it’s been true throughout big chunks of history, death records show.

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    If you’ve recently been to an elderly-care community, you’ve probably noticed the female survival advantage up close. At ages 65 or older, women outnumber men by a ratio of four to three; at ages 80 or above, it’s nearly two women for every guy. “Women,” Austad noted in his much-cited 2006 research on the gender longevity gap, “do not live longer than men because they age more slowly, but because they are more robust at every age.”

    I first heard something like this the day my daughter was born. She came into the world seven weeks premature. Weighing less than three pounds, Teodora was born with a rare disease that required, on day three of her life, complicated surgery to connect her esophagus to her stomach, and patch a hole in her trachea. It was like operating on a tiny bird, a doctor would later tell me. As my wife was still recovering from the delivery in another hospital across town, I faced Pietro Bagolan, the head of the neonatal surgery unit, at a children’s hospital in Rome, alone, and a bit overwhelmed. He explained Tea’s condition to me, took me through the upcoming procedure, and then shared an observation that I found, in that moment, more puzzling than reassuring. “Don’t worry,” he said. “She’s a girl. Girls make it.”

    He was right, thank goodness. Tea made it. With flying colors. Despite her myriad medical issues, she’s delightfully active and upbeat — mischievous, even, like most 8-year-olds. She has a surprisingly lively fastball. And, like most Warners, she’s an enthusiastically terrible dancer. Still, for years, I couldn’t get that conversation with Bagolan out of my head. Are baby girls better equipped — wired even — to brush aside mortal threats, even from day one? Later, when I pressed him for further explanation, he elaborated. The odds of survival are far better if the child is a fighter, he told me, adding “girls, more often than not, are fighters.”

    When I began to share Tea’s story with Austad, he practically finished it for me. “I know!” he exclaimed. “It’s one of these things that neonatologists all know, but they don’t normally talk about it. I’ve had dozens of them tell me the same thing: ‘Little girls make it. Little boys don’t.’ And we’re talking about a long time before there are any known hormonal differences between them. So, it’s really mysterious why there’s this difference in robustness.”

    The robustness of baby girls is hardly a modern-day phenomenon, we now know. In a study published in the journal PNAS in January, researchers broke down the male-female mortality rates of some of the most at-risk populations in history, including those who lived through the Irish potato famine of the 19th century and, from a generation before that, the largely doomed community of freed American slaves who returned to Africa, to present-day Liberia. In these populations, death records showed women consistently lived longer, on average, than men. “Most of the female advantage was due to differences in mortality among infants: Baby girls were able to survive harsh conditions better than baby boys,” the researchers wrote.

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    “Even in Liberia,” the researchers continued, “the population with the lowest life expectancy, newborn girls were hardier than newborn boys. That females survived more than males even at the infant ages, when behavioral differences are minimal, lends support to a biological underpinning of the female survival advantage.”

    Are baby girls better equipped — wired even — to brush aside mortal threats, even from day one?

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    To better understand the biological underpinning to aging and longevity, scientists often start with the oldest people on earth, centenarians. By 2050, it’s estimated there will be between 500,000 and 4 million centenarians on the planet. One of the world’s largest and most comprehensive ongoing studies on centenarians and their families is overseen at Boston Medical Center by Perls. There are roughly 4,000 subjects enrolled in the study. Just 30 percent are men. “Among the centenarians, it’s about 20 percent,” he notes. There are a few theories why the gender gap is so acute this late in life. It could be the protective power of estrogen on the immune system. Or it could be chromosomal. Born with two X chromosomes, women have a perfect copy of their genes (men do not). This is particularly helpful then to compensate against a potentially harmful gene mutation. These are but some of the questions advanced aging studies try to answer.

    Centenarians can tell us as much about the future as the past. Crack the code on the biology of the centenarian, the thinking goes, and you crack the code on aging itself. “The hope,” Perls says, “is to translate these discoveries into a much better understanding of what it takes to age so well, to avoid or delay diseases like Alzheimer’s and discovering drugs and other strategies to slow aging and delay or escape aging-related diseases.”

    But that’s not to say it’s all downhill for men. For example, researchers note something called “gender crossover,” (sometimes, it’s referred to as the “mortality-morbidity paradox”) which finds that men older than 90 tend to be more physically and mentally acute than their female counterparts, suggesting that through the study of the oldest of old men we can learn much about maintaining a high quality of life at advanced age.

    For decades, Belgian demographer Michel Poulain has been studying blue zones, population centers where the inhabitants live to extreme ages. One such blue zone is the town of Villagrande Strisaili in the mountains of Sardinia, the Mediterranean island famed for its spectacular beaches, its savory pecorino cheese, and its surprising number of triple-digit old-timers.

    In 2011, Poulain published in The Journal of Aging Research research documenting how Villagrande Strisaili has something akin to a fountain of youth keeping the white-haired locals fit and healthy. Here, there were 10.8 centenarians per 1,000 newborns — more than double the rest of the island. Yet the longevity trend there was upside down. Of the 30 Villagrande centenarians he studied, 16 were men. He wondered if it was a case of epigenetics — the phenomenon in which diseases, environmental stresses and other factors switch certain genes on and off, potentially impacting adaptation. Epigenetic changes in gene expression that favored longevity could have been passed down from generation to generation. Or, was the men’s unique lifestyle the saving factor? The men of the village were predominantly shepherds who roamed the hills with their flock, away from the family for months at a time. They were locavores, getting their meat, dairy and greens from their flock and from the lands they traversed. These men had plenty of fresh air and exercise, and had little time for booze or cigarettes. He also noted their daily routine was relatively stress-free.

    Still, he said, “the recommendation is not to go and live like a shepherd in Sardinia.” The secret to male longevity is more complicated than ditching the rat race for a life of Sardinian simplicity. If anything, the Sardinian shepherds of Poulain’s study reinforce the well-established theory that the secret to longevity involves a combination of factors. Namely, “it’s what you inherit from your parents and grandparents,” Poulain says, “and what you contribute yourself through lifestyle choices.” But there is an implicit feel-good message in that: the decision to eat better, quit smoking, eliminate stress and drinking to excess is not just good for you, it’s good for your progeny. In fact, given the importance of epigenetics to longevity, the switch to clean-living habits could very well benefit your offspring more than you. If that comes across as overly maternalistic advice, so be it.

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    The “grandmother hypothesis” offers an explanation for why female humans live for decades after the onset of menopause while other large female primates die off soon after their fertile years come to an end. Anthropologist Kristen Hawkes contributed much of the hard data to this theory. Her take: Because grandmas are needed to help raise their kids’ kids, they play an evolutionarily vital role in the survival of the entire human species. The grandmother hypothesis has held up well under scrutiny. But it doesn’t say much about why a biped like me will reliably be outlived by my wife, let alone how we men can begin to narrow the gap.

    However incomplete, the grandmother hypothesis still offers helpful insights about how our species has evolved — and, moreover, how it’s evolved to age and endure — in such a profoundly inequitable way. It comes down to female reproduction and genes, says Perls. He believes our species has adapted to live longer and longer so that women can continue to have children at a relatively late stage of life, into their 40s, and then care for them well beyond that.

    “This is the evolutionary driving force for why we’re able to live to older age,” he says. “Men are pretty superfluous to all this.”

    The gender longevity gap may narrow. But, thanks to evolution, it’s unlikely to disappear. Both sexes depend on it.

    Bernhard Warner is an American journalist based in Rome. Follow him on Twitter @bernhardwarner.