The fact women are living longer than men doesn't necessarily mean they are living better. Illustration / New York Times
The fact women are living longer than men doesn't necessarily mean they are living better. Illustration / New York Times
By understanding the reasons, scientists hope to help both sexes age better.
Women outlive men, by something of a long shot: in the United States, women have a life expectancy of about 80, compared with about 75 for men.
This holds true regardless of where womenlive, how much money they make and many other factors. It’s true even for most other mammals.
“It’s a very robust phenomenon all over the world, totally conserved in sickness, during famines, during epidemics, even during times of starvation,” said Dr Dena Dubal, a professor of neurology at the University of California, San Francisco.
But the reasons women live longer are complicated and less established – and the fact they are outliving men doesn’t necessarily mean they are living better. Women tend to have shorter health spans (the number of healthy years a person lives) than men, said Berenice Benayoun, an associate professor at University of Southern California’s Leonard Davis School of Gerontology. Women are generally more physically frail than men in old age; they’re also more vulnerable, particularly after menopause, to developing cardiovascular issues and Alzheimer’s disease, in part because age itself is a risk factor for those conditions, Benayoun says.
Scientists are trying to uncover the reasons men and women age differently in the hopes of extending lifespan and health span for both.
“If we can understand what makes one sex more resilient or vulnerable, then we have new pathways, new molecular understanding, for new therapeutics that could help one or both sexes also be resilient,” Dubal said.
Here’s what they know so far about what causes the longevity gap.
Women in the US on average live about five years longer than men. Photo / 123rf
Genetics
A growing body of research suggests the XX set of female sex chromosomes (which, with other chromosomes, carry our DNA) may impact longevity, though it’s not clear exactly how. For example, a 2018 study conducted by Dubal’s lab looked at genetically manipulated mice with different combinations of sex chromosomes and reproductive organs. Those with two X chromosomes and ovaries lived longest, followed by mice with two X chromosomes and testes. Mice with XY chromosomes had shorter lifespans.
“There was something about the second X chromosome that was protecting the mice from dying earlier in life, even if they had testes,” Dubal said. “What if there was something on that second X chromosome that was in some ways a sprinkle of the fountain of youth?”
Scientists haven’t yet examined this in humans, but Dubal said the fact we have the same hormones and sex chromosomes, and similar reproductive systems, suggests the findings could be similar in people.
Epigenetic factors – environmental or lifestyle elements like climate or chronic stress that impact which genes are expressed, and how – may also play a role in life span, widening or shrinking the disparities between men and women, said Montserrat Anguera, an associate professor of biomedical sciences at the University of Pennsylvania School of Veterinary Medicine who studies this topic.
The second X chromosome may offer protective health benefits in women. Photo / 123rf
Hormones
Researchers are also investigating the role of sex hormones like oestrogen in longevity and are especially interested in the effect they have on the immune system. “There’s decent data showing that, at least before menopause, the female immune system tends to be better, more on it and better able to mount responses,” Benayoun said. In general, males “tend to do much worse in response to infection”, which in turn could shorten their lifespans; they’re also more likely than women to die of sepsis, she said.
One 2017 analysis found women who experienced menopause later in life – older than 50 – lived longer than those who experienced it earlier. When oestrogen levels drop, such as during menopause, women’s immune systems seem to weaken. And women tended to catch up to (or surpass) men in terms of developing diseases that were less common before menopause, Benayoun said.
Women’s immune systems tend to be stronger before menopause due to oestrogen. Photo / 123rf
Lifestyle and behaviour
Behavioural patterns play a key role in the disparity. Women are generally less likely than men to smoke or drink heavily – behaviours that contribute significantly to mortality, says Kyle Bourassa, a psychologist and a senior fellow at the Centre for the Study of Ageing and Human Development at Duke University.
Women also tended to practise more “health-promoting behaviour” like wearing a seatbelt or going to the doctor for annual check-ups, Bourassa said. He said women are more likely than men to socialise, protecting them from the detrimental effects of social isolation and loneliness. A 2023 analysis found they’re also less likely to die by drug overdose or suicide.
Social connections contribute to longevity and women tend to maintain stronger networks. Photo / 123rf
External factors
On a broader societal level, issues like war or gun violence disproportionately impact men, says Naoko Muramatsu, a professor of community health sciences at the University of Illinois Chicago.
During the Covid pandemic, men died at higher rates than women. Research showed they were more likely to hold jobs that exposed them to the virus, such as food preparation or construction, or to be homeless or incarcerated, all of which affected mortality rates.
Ultimately, it was a combination of all these factors that determined the lifespan gap, said Alan Cohen, an associate professor of environmental health sciences at Columbia University Mailman School of Public Health. “There’s probably a thousand ways that that’s happening.”
Even though we did have control over some factors, like drinking, smoking and diet, it was not yet clear how significantly longevity would be impacted by changing those behaviours, Bourassa said.
“We need randomised control trials to tease these things apart,” he said.
