In search of why women live longer than men

UNITED STATES – Women outlive men, by something of a long shot: In the United States, women have a life expectancy of about 80, compared with around 75 for men.

This holds true regardless of where women live, how much money they make and many other factors. It is even true 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 that they are outliving men does not necessarily mean they are living better. Women tend to have shorter healthspans – the number of healthy years a person lives – than men, said Dr Berenice Benayoun, an associate professor at the USC Leonard Davis School of Gerontology.

Women are generally more physically frail than men in old age. They are 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, she added.

Scientists are trying to uncover the reasons men and women age differently in the hopes of extending lifespan and healthspan 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,” Dr Dubal said.

Here is what they know so far about what causes the longevity gap.

Genetics

A growing body of research suggests that the XX set of female sex chromosomes – which, along with other chromosomes, carry the DNA – may impact longevity, though it is not clear exactly how.

For example, a 2018 study conducted by Dr Dubal’s laboratory 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,” Dr 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 have not yet examined this in humans, but Dr Dubal said the fact that people have the same hormones and sex chromosomes, and similar reproductive systems, suggests that the findings could be similar.

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 lifespan, widening or shrinking the disparities between men and women, said associate professor of biomedical sciences Montserrat Anguera at the University of Pennsylvania School of Veterinary Medicine, who studies this topic.

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,” Dr Benayoun said. In general, males “tend to do much worse in response to infection”, which in turn could shorten their lifespans. They are also more likely than women to die of sepsis, she said.

One 2017 analysis found that 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 tend to catch up to, or surpass, men in terms of developing diseases that were less common before menopause, Dr Benayoun said.

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, said psychologist Kyle Bourassa, who is a senior fellow at the Center for the Study of Aging and Human Development at Duke University.

Women also tend to practise more “health-promoting behaviour”, like wearing a seat belt or going to the doctor for annual check-ups, he said. In addition, he said that women are more likely than men to socialise, protecting them from the detrimental effects of social isolation and loneliness. A 2023 analysis found they are also less likely to die by drug overdose or suicide.

External factors

On a broader societal level, issues like war or gun violence disproportionately impact men, said Dr Naoko Muramatsu, a professor of community health sciences at the University of Illinois Chicago.

During the Covid-19 pandemic, men died at higher rates than women. Research showed that they were more likely to hold jobs that exposed them to the virus, like food preparation or construction, or to be homeless or incarcerated, all of which affected mortality rates.

Ultimately, it is a combination of all these factors that determines the lifespan gap, said Dr 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.”

And even though people do have control over some factors, like drinking, smoking and diet, it is not yet clear how significantly longevity would be impacted by changing those behaviours, Mr Bourassa said.

“We need randomised control trials to tease these things apart,” he said. NYTIMES