Women live longer than men even in the most extreme conditions

Women live longer than men even in the most extreme conditions

Young women resist better than males in times of famine, epidemics or slavery, although it is not clear why.

Jean Calment is the longest-lived person of which there is constancy. Born in 1875, he met Van Gogh, rode a bicycle and smoked most of his life. When he died in 1997, at 122 years, it was toyed that the next oldest living person was Lucy Askew, a 104-year-old British man. Your sex is no coincidence. Among those who reach the century of age, there are four women for each man. This superiority in life expectancy is maintained at any point on the planet. They tend to live several years longer than they do, it is not clear why.

Now, a study has analyzed the mortality rate in groups subjected to famines, epidemics and slavery. His conclusions show that the females also resist better in these horrible conditions and uncover a surprising fact. Most of the advantage between them and them appears in the first year of life.

The greatest mortality recorded in history occurred in Liberia between 1820 and 1843. The U.S. government encouraged freed slaves to marchasen a new homeland in Africa. Many were only expected to die. 43% of the emigrants died in the year of arrival, probably due to infectious diseases. In those years, the life expectancy of a child born in Liberia was 1.68 years and that of a girl, 2.23, according to the study, published in the Journal of the National Academy of Sciences of the United States.

The work also analyses the deaths among slaves in the Caribbean island of Trinidad (Trinidad and Tobago) in the early nineteenth century, during famines in Ukraine in 1933, Sweden between 1772 and 1773 and Ireland between 1845 and 1849, and two measles epidemics in Iceland in 1846 and 1882. Only cases are considered in which the life expectancy of one or both sexes fell from the age of 20. "We have only found documented cases of the past because, fortunately, it is now very unlikely that, even in the worst crises, life expectancy will be 20 years or less," says Virginia Zarulli, researcher at the Max Planck Centre in Odense ( Denmark) and the first author of the study.

In almost all cases analyzed, women lived longer than men. The advantage goes from the more than half year of life in the worst case (Liberia) to 3.7 years more in the best (Ireland). The only exception is among the slaves of Trinidad, something that Zarulli and his team attributed to that men were considered more valuable to work in the field and therefore cared more. The majority of women's survival advantage over men is given during the first year of life, after which differences between sexes are attenuated. In Liberia, Trinidad, Iceland and Ireland, this imbalance in infant mortality accounts for up to 50% of the entire divergence. In more recent disasters, such as the famine that followed World War II in the Netherlands and others registered in Asia, a similar advantage is seen.

"Under normal conditions, child mortality tends to be higher than that of girls, so the natural proportion is about 107 children born per 100 girls," explains Zarulli. "The huge difference we have encountered in favor of women during crises is very surprising. What is known about the Times studied is that, if there was a preferential treatment for sexes, the males were the beneficiaries, so it is even more remarkable that despite possible discrimination the girls survive more, "he argues.

The authors believe that this superiority has a biological explanation. In similar living conditions, females always live longer, as several studies have shown, including one among cloistered monks and nuns in Bavaria (Germany), with an advantage of up to one year of life. Among the majority of mammals, including primates, both wild and captive, females also live significantly more time. Sex hormones can be part of the explanation, the study points out. Female estrogens are anti-inflammatory and protect the circulatory system, while testosterone is associated with increased mortality from some diseases. estrogens strengthen the immune system, while testosterone and progesterone seem to do the opposite. The incidence of infections is lower among women than men (most deaths in the analyzed populations may attributed to dysentery, starvation, and diarrhea). Along with these biological factors there are other social ones that have been helping the female sex, as they smoke, drink and drug less, drive less recklessly, take better care of their diet and have fewer risky behaviors.

"The fact that among babies, when differences in behavior are minimal, girls sobreviviesen much more seems to point out that the female advantage has a well-established biological roots," says Zarulli. "At the risk of oversimplifying, we can easily see how, to survive, an imaginary tribe needs only a few men, but many more women. A single man can have many children, but the number of babies that can raise a woman is limited, "he says.

If they had taken into account not only the births, but the conceptions, something complicated to find in the registers, the female superiority would be even greater, because "for every 100 females are conceived about 160 males", explains Diego Ramiro, demographer of the Higher Council of Scientific Research. "This work comes to show that women are strong sex, although because they live more also suffer more aches," he adds.

The two investigators who have conducted the research, Kaare Christensen, of the University of Southern Denmark, and James Vaupel, founder of the Max Planck Center for Demographic Research in Rostock (Germany), have been studying the biological fundamentals for years of aging and the limits of human longevity. According to Vaupel there is no age limit set for our species — a statement discussed by other experts — and it is to be expected that 10 years of life expectancy will continue to be gained every 40 years. If this is true, it is to be expected that women will continue to take advantage for a long time.