Why females have longer life expectancy?

Pseudoexfoliation and Cataract Syndrome Associated with Genetic and Epidemiological Factors in a Mayan Cohort of Guatemala.

Hicks PM, Au E, Self W, Haaland B, Feehan M, Owen LA, Siedlecki A, Nuttall E, Harrison D, Reynolds AL, Lillvis JH, Sieminski S, Shulman JP, Barnoya M, Noguera Prera JJ, Gonzalez O, Murtaugh MA, Williams LB, Farkas MH, Crandall AS, DeAngelis MM. Hicks PM, et al. Int J Environ Res Public Health. 2021 Jul 6;18(14):7231. doi: 10.3390/ijerph18147231. Int J Environ Res Public Health. 2021. PMID: 34299682 Free PMC article.

HEIDI DOUGLASS |

Yes, it’s true.  Women live longer than men.  In fact not only does evidence suggest that we females have always outlived the blokes, it appears that as more time passes the gap is increasing.  Currently Australian women can expect to live, on average, 5 years longer than our male counterparts, which is the same for most developed nations of the world.  Why is this so?

No-one knows for sure, but there are a number of theories.  According to CHeBA’s Co-Director Professor Perminder Sachdev, the first thing that people will say about this topic is that women have healthier habits and he thinks to some extent this is true.  Women tend to smoke less, drink less, eat better and generally take care of their bodies.  This may be a factor, but according to Professor Sachdev this isn’t a sufficient explanation because of a paradox, which is that even though women live longer than men, statistics show that they acquire more illnesses and visit doctors more than men. 

So what about stress?  Historically men have had the stress of going to work everyday to support the family and had to periodically go off and fight wars.  Surely “life stress” has hindered men?  Apparently not.  Even though women’s lives have increased in stress with the elimination of male-female role stereotyping in the second half of the century, and the combined pressures of work and home on women, they still manage to live longer.  Hence, stress isn’t a good explanation either.  So what is?

I posed this question to my family, who, despite being in long and (so I thought) loving relationships, were all fairly cynical about the longevity of women.  One family member told me: “They need to see their husbands die and the power of will is amazing”.  No, that didn’t come from a female.    

My surrogate grandmother, a mid-70s German that has lived in Australia for more than 50 years, made some sense.  According to her, “there are biological differences related to hormones and childbearing [that make women live longer].  They are also better equipped to cope, and when husbands die earlier can look after themselves better than widowed men.”

My sister-in-law also made an interesting point, stating that “women are less susceptible to cell damage which is also why more girls are born than boys.”

My partner, in the health and fitness industry, may also be close to the mark with his statement that “women store body fat differently to men.  The theory is that men immediately store body fat around their internal organs whereas a woman tends to store it in their hips and thighs (to protect the child bearing process).  This disadvantage to men does not tend to affect women to the same extent until after menopause.”

My sister, (married for 15 years with four children), thinks it is “because we have more heart”. According to my mum women are just waiting a very long time for a break.  And from my dad?  Apparently "men can only take so much".      

Hmm…on that note, let’s head back to the expert. 

According to Professor Sachdev, we need to try to understand why we age.  What are the processes at the biological level that make us age? 

“We need to understand this because when you look at other species like rats or chimpanzees - even in those species females tend to have an advantage over males,” he says. 

“A female rat in a laboratory will live longer than males.  The female or worker honeybee lives a relatively long life whereas the male counterparts only live for a day or 2, with the express purpose of mating with the queen bee, and this is true of a number of other species as well.” 

“People have looked at the reasons for this from various viewpoints.  One popular theory for ageing is the wear and tear theory; that as cells divide, some defects accumulate in the cell, both in the DNA and the proteins that are formed.  The body has a mechanism by which you can repair these defects and it is suggested that women do a better job of repairing these defects at a cellular level than men, and gradually with ageing the individuals that have a better repair mechanism will survive longer than those that do not.  Hence, a major reason for women living longer than men is at the genetic level. And an obvious and major difference at the genetic level for women is that they have two X Chromosomes whereas men only have one X chromosome.  The second major difference is in the hormones themselves.  Women have oestrogen as a major hormone through their adult lives rather than testosterone - although of course after menopause that changes for women.”

It would appear that while testosterone gives men advantages in early life such as in increased muscle strength, it may actually be at a long-term cost for ageing.  Oestrogen early in life is, on the other hand, a key factor in providing protective effects from the wear and tear mechanisms that are inevitable in the body. 

According to Professor Sachdev, it has been shown that male animals have a tendency to live longer if they have been castrated.  Scary thought for men!  Historical evidence suggests that castrated men tend to live longer than uncastrated ones by about 14 years. 

The fact is that a female child born today is likely to live into the early 90s, with far more women reaching this age than men.  Western societies continue to see an increase in the lifespan and no one knows how far that will go.  So far the longest living person (a woman) with a well-documented age died at 122.

Australia’s only study of centenarians is conducted by the Centre for Healthy Brain Ageing (CHeBA).  With the centenarian population being the fastest growing demographic and predictions that by 2050 there will be over 2 million centenarians internationally (with up to 50,000 in Australia), it is worth finding out why this is so.  And why the majority of centenarians are women. 

As Professor Sachdev says, “It is not without reason that we call nature Mother Nature”.

Women live longer than men across the world and scientists have by and large linked the sex differences in longevity with biological foundation to survival. A new study of wild mammals has found considerable differences in life span and aging in various mammalian species.

Among humans, women’s life span is almost 8% on average longer than men’s life span. But among wild mammals, females in 60% of the studied species have, on average, 18.6% longer lifespans. The ratio is considerably different for different groups of mammals.

An international team of scientists led by Jean-François Lemaître, from the University Lyon 1 in France, collected information on age-related mortality for 134 populations of 101 wild mammalian species.

“It was surprising to observe that this gender gap in lifespan often exceeds the one observed in humans and is, at the same time, extremely variable across species,” said Lemaître.

"For example, lionesses live at least 50% longer in the wild than male lions,” said Tamás Székely, from the University of Bath, one of the authors of the study.

“We previously thought this was mostly due to sexual selection - because males fight with each other to overtake a pride and thus have access to females, however our data do not support this,“ said Székely.

Scientists have found that even though females consistently live longer than males, the risk of mortality does not increase more rapidly in males than in females across species. Therefore, they say, there must be other, more complex factors at play, such as environmental conditions in which the animals live and sex-specific growth, survival and reproduction through the history of the species.

For example, the authors of the study say, roaming males could be exposed to more environmental pathogens. This was noticed in three populations of the bighorn sheep.

The magnitude of the lifespan gap could also be shaped by local environmental conditions with a trade-off between reproduction and survival. In some species, males allocate more resources to sexual competition and reproduction, which, scientists say, could lead to bigger sex differences in lifespans.

"Another possible explanation for the sex difference is that female survival increases when males provide some or all of the parental care,“ said Székely. “Giving birth and caring for young becomes a significant health cost for females and so this cost is reduced if both parents work together to bring up their offspring."

In order to measure the extent to which biological differences between the sexes affect life expectancy, scientists plan to compare the data on wild mammals with the data on mammals kept in the zoo, where they do not have to fight with predators or compete for food and mates.

Scientists hope the findings will contribute to better understanding of what affects human longevity. In the past 200 years, the average life expectancy of humans has more than doubled due to improved living conditions and advances in medicine. Yet women continue to live longer than men, suggesting the biological differences also have a role.

According to the U.S. Centers for Disease Control, the average American man will live to age 76, while the average woman in America will live to age 81. Women can also expect to be healthier than men in their senior years. Experts shave said the gap is due to a combination of biological and social differences.

Men’s hormone testosterone is linked to a decrease in their immune system and risk of cardiovascular diseases as they age. It is also linked to risky behavior: smoking, drinking and unhealthy eating habits. If diagnosed, men are less likely than women to follow doctor’s advice. Statistics show that men are more likely to take life-threatening risks and to die in car accidents, or gun fights.

Authors of the new study say the differences between male and female longevity are shaped by complex interactions between local environmental conditions and sex-specific reproductive biology. They say that more research is likely to provide “innovative insights into the evolutionary roots and physiology underlying aging in both sexes.”