Science, Art, Litt, Science based Art & Science Communication

Krishna: They say numbers don’t lie!

What you said is usually the trend in the world but in some developing countries men outlive women. This is because of poor nutritional statuses of women, child marriages, and other cultural conditions in these countries.

Why do women outlive men in general?

The answer lies in our natural evolution. Of course, social and lifestyle factors do have a bearing, but there does appear to be something deeper engrained in our biology.

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.

Among the other contributory things is the “jogging female heart” concept – 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. Or 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 and 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 are supposed to face more long-term damage.

Then hormone differences. More testosterone in men might make their bodies stronger in the short-term, but the same changes also leave them open to heart disease, infections, and cancer later in life. Testosterone might increase seminal fluid production but promote prostate cancer; or it might alter cardiovascular function in a way that improves performance early in life but leads to hypertension and atherosclerosis later. Male sex hormones also decrease immune function . 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. The female sex hormone oestrogen acts like an ‘antioxident’, meaning that it mops up toxic chemicals that cause cells stress. In animal experiments, females lacking oestrogen tend not to live so long as those who have it. 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. The nature itself protects women because they have to do important tasks: child bearing and child rearing. 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.

One recent study found that, after the age of 65, men lose antibody-producing B cells in their blood—but women didn't experience the same loss. The researchers also found that men experienced greater blood inflammation as they aged, a factor that is associated with serious cases of diseases.

Moreover, 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. On top of all that, men are more likely to take life-threatening risks and to die in car accidents, brawls or sword and gun fights. There’s evidence 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 has found that elevated testosterone levels are associated with risky behaviours.

And women in several modern cultures and countries do very hard physical work, at home and outside too unlike earlier times.

All these things contribute to a woman’s longevity.

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