Things that Yoram knows: sick, dying, widow - why women live longer than men

Judith asks: "Why do women live longer than men?"

If there is an area where female supremacy is not in doubt, it is life expectancy. Women live longer than men Almost anywhere in the world and at any time. Every year, more boys than girls are born in the world (about 105 boys to 100 girls), but the gender ratio is constantly changing in favor of women up to the oldest age group: the 110-year-olds and over, which only one in 3 million people will get to reach. In total, about 600 people have celebrated 110 springs to date, about 90% of them women. The list of the 50 oldest people at the time of writing is entirely female.
Female longevity is an enigma because women get sick more than men, need more sick leave, are hospitalized more, and yet in every age group the male mortality rates exceed the female. As expected from such a complex puzzle there is no agreed upon answer and apparently there is also no single reason for female strength and science provides plenty of explanations to choose from.

Everything in the gardens?

Of course, there are those who blame the immediate suspect: the Y chromosome. As you remember, women have two copies of this chromosome, while men have to make do with only one, so a defect in the gene of the X chromosome will always cause harm in the man. In women, one of these chromosomes is silenced in each cell, but if one X chromosome is severely damaged, then neighboring cells, in which the active chromosome is normal, will reproduce at the expense of the damaged cells, so that a woman can live well even if a harmful mutation in this chromosome. Proponents of this theory point to examples from the animal world that reinforce this connection. Thus, for example, in some species of birds where the females actually have a chromosome that does not have a partner, the males are the species that lives the longest in captivity. In marsupials, the same X chromosome (the one that originates from the father) is silenced in the female, in every cell of the body, so that there is no possibility for a normal chromosome to cover its defective friend, and in some kangaroo species in zoos, females do not have an advantage over males in life expectancy. Comparing the difference in life expectancy among 344 species of vertebrates revealed a clear statistical correlation: the species with 2 identical sex chromosomes tends to live longer even among reptiles and reptiles. But the animal world insists on providing exceptions as well: in some mammals and indeed quite common ones such as mice and bats the males live longer than the females even though they, like us, carry the X and Y chromosomes.

Another dubious type on the dock is the male sex hormone - testosterone. An old theory links this hormone to suppression of the immune system. Testosterone, according to this theory, weakens the immune system and diverts resources to external signs (such as peacock feathers or elk horns) and to aggressive behavior aimed at controlling the harem. For example, it turns out that moose high in testosterone in the wild have stronger antlers, bigger testicles and more sperm, but also more parasitic worms. In the opposite direction, it was demonstrated that in order to treat the infection, males lower the level of testosterone and with it, prominent feather and beak colors fade in male ducks. Some have even suggested that the prominent sex marks used by males for courtship are a signal to females of an abundance of testosterone, i.e. of the candidate's ability to survive with a dormant immune system. This idea has not received much support and the relationship between testosterone and immune response is probably complex, indirect and ambiguous. In addition, for people in the developed world, infectious diseases are not an important cause of death, yet the difference in life expectancy between men and women, about five years, shows no signs of diminishing

the mother's curse

We receive the hereditary material in the cell nucleus equally from mother and father, but the DNA in the mitochondria originates in the egg cell only. A mutation in the mitochondria that affects males will therefore be somewhat "transparent" to natural selection and will therefore be able to spread in the population more than such mutations that affect both sexes. The problem is that the "mother's curse" theory predicts a lifespan gap in favor of the female in all species of animals and as we have seen there are quite a few in which the males actually live longer. The mitochondrial genome is small and damage to it will usually harm anyone who carries the mutation. In plants where the mitochondrial genome is richer and the plant receives from the mother, in addition to the mitochondria, also a chloroplast (the organelle of photosynthesis) with its own genome, there is indeed confirmation of the "mother's curse".

The theory of the male world

At young ages, the main female advantage stems from men's insistence on killing themselves in accidents in fights and wars. The responsibility for fatal behavioral differences falls partly on the shoulders of testosterone and partly on the macho culture (driven by testosterone-washed minds). In mammals in the wild, most of the difference in favor of females (in those species where they live longer) is attributed to struggles for control and territory between males. The competition pushed the males to increase their body size and add showy and oppressive additions such as large horns, formidable fangs or a cumbersome peacock tail. A larger body is also more vulnerable and requires more oxygen, which creates cell defects over time. In humans, women and men, life expectancy decreases with height so the difference in height between men and women can explain part of the life expectancy gap.  

A comparison between different species shows a consistent trend: the more polygamous the lifestyle, i.e. the more reproduction falls on the shoulders of a few males who control large harmonies, the more difficult the competition between the males is and they die younger than the females. Among the monogamous, who are loyal to one female, there is almost no difference in life expectancy and sometimes even the males live longer than their partners.

Differences in size and energy consumption

 Science knows only one way to extend life expectancy: Eat less. In addition to the obvious damages of obesity and diabetes, the more food and oxygen we consume, the more active oxygen atoms we create in each cell that damage DNA. Oxidative damage accumulates and is linked to cardiovascular diseases - the main cause of death in the Western world. There are mechanisms in the cell whose job it is to neutralize these toxic byproducts of breathing and it turns out that they work better in women.

Longevity mutations have been discovered in laboratory animals that are beloved by geneticists. These are related to a very small group of genes responsible for cell response to hormones such as insulin and insulin-like growth hormone (IGF-1). These genes produce proteins that control the expression of a large number of other genes involved in metabolism, detoxification, control of oxidative damage, and immune responses. The less active these hormones are, the longer the lifespan and this often involves less growth and less fertility. This is a system that works with minor changes throughout the animal kingdom and aims to respond to conditions of distress and shortages by slowing down growth processes and energy consumption.

Studies on large populations of old men and women confirm that, as in the case of fruit flies and worms in the laboratory, these genes also have a significance in extending life span. Extreme old age will be awarded to those who spend most of their time in slow motion even in times of abundance. In women, the response to these hormones is slower, the metabolism is slower and the difference is related to differences that greatly affect diseases of old age such as obesity and blood glucose concentrations. Men, therefore, will grow more, eat more, burn more oxygen and suffer more from the side effects of this vigorous activity. In addition, men are taller and heavier than women, which means they go through more cell divisions that erode the chromosomes.

Men kill themselves

In humans, accidents and violence certainly play a role in the mortality gap, but it only explains the differences among young people, and women continue to die less than men even in old age when the walker takes the place of the motorcycle. It is possible, however, that the burden of competition imposed more on men continues to take a toll throughout life.

Biologist Anders Møller examined the difference in life expectancy in different societies and found that the more equal the income distribution (a characteristic expressed in the famous Gini index) the smaller the gap between the sexes and the larger the Gini index (less egalitarian society) the earlier the men die compared to the women in the same population. The trend is maintained, regardless of the absolute size of the economic pie (which affects overall life expectancy but not the gap between men and women). The assumption is that the bigger the gaps, the more men are forced to fight for their relative place on the scale and this burden on young breadwinners takes its toll in disease and mortality. A more egalitarian society might benefit men, but the Gini index can only explain about 10% of the life expectancy gap to the detriment of men. Differences in behavior between men and women, on the other hand, can explain quite a bit: women go to doctors more often both in case of illness and proactively for tests and follow-up, after the visit they are more careful to take their medications and listen more to instructions related to diet and physical activity. They smoke less, drink less and drive more carefully. statistical model brought up that these behavioral differences throughout life can explain no less than 3.2 years difference in life expectancy out of the average difference of 4.6 years in favor of women in the rich countries.  

Thanks to Dr. Anders Møller and Dr. Steven N. Austad for their help.

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More of the topic in Hayadan:

• Life expectancy in Israel in 2016: 80.7 years for men and 84.2 for women
• Who is for life and who is for death
• For every additional decade of life, the women gained two grandchildren