Why do women have longer life expectancy than men?
The survival advantage of women is seen in every country, in every year, for which reliable records exist
Over the past 70 years, the human life expectancy has risen 26.2 years, according to a research by Worldometers.
The study shows that In 1950, the life expectancy was for humans was 47 years with, with women having a life expectancy of 48.5 years and men 45.5 years; that risen to 73.2 years now with men having a life expectancy of 70.8 years and women having a life expectancy of 75.6 years.
From the country with the highest life expectancy to the one with lowest, women tend to live longer than men; a phenomenon that has been going on since humans emerged.
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"This gender gap in life expectancy is true for all societies, and it is also true for the great apes," said Dr Perminder Sachdev, a professor of neuropsychiatry at the University of New South Wales in Australia who has studied human longevity, reports the TIME magazine.
The World Health Organization's HALE index, which calculates the number of years a man or woman can expect to live without a major disease or injury, found out that women have longer healthy years compared to men.
The survival advantage of women is seen in every country, in every year, for which reliable records exist. In fact, the difference in lifespan has remained stable even throughout monumental shifts in society.
"This remarkably consistent survival advantage of women compared with men in early life, in late life, and in total life is seen in every country in every year for which reliable birth and death records exist. There may be no more robust pattern in human biology," an article in Karger journal said.
"Men are more likely to smoke, drink excessively and be overweight. They are also less likely to seek medical help early, and, if diagnosed with a disease, they are more likely to be non-adherent to treatment," Dr Sachdev said, adding that men are more likely to take life-threatening risks and to die in car accidents, brawls or gun fights.
One early idea was that men work themselves into an early grave. Whether working in a mine or ploughing the land, they put extra stress on their bodies and amassed injuries that caught up with them later in life.
Behaviour and biology
Factors such as smoking, drinking, and overeating may partly explain why size of the gender gap varies so widely between countries. But the fact is that female chimpanzees, gorillas, orangutans, and gibbons also consistently outlive the males of the group.
"Social and lifestyle factors do have a bearing, but there does appear to be something deeper engrained in our biology," said Tom Kirkwood, who studies the biological basis for ageing at Newcastle University in the UK.
It would seem like the answer lies in evolution. There are many potential mechanisms – starting with the bundles of DNA known as chromosomes within each cell. Chromosomes come in pairs, and whereas women have two X chromosomes, men have an X and a Y chromosome. That difference may subtly alter the way that cells age. Having two X chromosomes, women keep double copies of every gene, meaning they have a spare if one is faulty. Men don't have that back-up. The result is that more cells may begin to malfunction with time, putting men at greater risk of disease.
A woman's heart rate increases during the menstrual cycle, offering the same benefits as moderate exercise. The "jogging female heart" hypothesis – the idea that a woman's heart rate increases during the second half of the menstrual cycle, offering the same benefits as moderate exercise. The result is delayed risk of cardiovascular disease later in life.
Study suggests that a man's biology—namely, his elevated levels of the male sex hormone testosterone—may lead him into the kind of trouble that could shorten his life.
Research from Duke University has found that elevated testosterone levels are associated with risky behaviors, reports the BBC.
Experts say testosterone may abbreviate a man's lifespan in other ways. Not only do women escape the risks of testosterone – they may also benefit from their own "elixir of youth" that helps heal some of the ravages of time.
"Male sex hormones decrease immune function and increase the risk for cardiovascular diseases," said Kyung-Jin Min, a professor of biological sciences at Inha University in South Korea.
While the links between testosterone and immune function aren't clear, Min's study points to lab research showing that testosterone may block the release of some disease-fighting immune cells.
There is also a good amount of research linking low levels of testosterone to heart disease and poor health outcomes in men.
It may well be that a man's hormones aren't to blame; instead, a woman's hormones may offer her some added lifespan benefits.
A 2013 review in the International Journal of Endocrinology found evidence that estrogen can prevent the kind of DNA damage that leads to disease. That review also turned up evidence that estrogen can help maintain normal, healthy cell function.
"Estrogen appears to be protective—it has been shown to have an antioxidant role," said Dr Sachdev.
"All this is entirely speculative. Once children are born, men are disposable," Dr Sachdev said.
"But the robust body of the mother is important for the survival of the offspring."
The female body's historical role as child-rearer may also be a factor. A woman's body has evolved to withstand and bounce back from the physical trauma of pregnancy and childbirth, as well as the demands of breastfeeding—challenges to which a male's body is never exposed.
Size matters
It could also be a simple matter of size. Taller people have more cells in their bodies, meaning they are more likely to develop harmful mutations; bigger bodies also burn more energy, which could add to wear and tear within the tissues themselves. Since men tend to be taller than women, they should therefore face more long-term damage.
