text: Credit: George Hodan/public domain Across the entire world, women can expect to live longer than men. But why does this occur, and was this always the case? 
   
   According to a new study led by University of Southern California Leonard Davis School of Gerontology researchers, significant differences in life expectancies between the sexes first emerged as recently as the turn of the 20th century. As infectious disease prevention, improved diets and other positive health behaviors were adopted by people born during the 1800s and early 1900s, death rates plummeted, but women began reaping the longevity benefits at a much faster rate. 
   
   In the wake of this massive but uneven decrease in mortality, a review of global data points to heart disease as the culprit behind most of the excess deaths documented in adult men, said USC University Professor and AARP Professor of Gerontology Eileen Crimmins. 
   
   "We were surprised at how the divergence in mortality between men and women, which originated as early as 1870, was concentrated in the 50 to 70 age range and faded out sharply after age 80," Crimmins said. 
   
   The study was conducted with USC University Professor and ARCO/William F. Kieschnick Professor in the Neurobiology of Aging Caleb Finch and Research Associate Hiram Beltrán-Sánchez of the Center for Demography of Health and Aging at the University of Wisconsin-Madison. It examined the lifespans of people born between 1800 and 1935 in 13 developed nations. 
   
   Focusing on mortality in adults over the age of 40, the team found that in individuals born after 1880, female death rates decreased 70 percent faster than those of males. Even when the researchers controlled for smoking-related illnesses, cardiovascular disease appeared to still be the cause of the vast majority of excess deaths in adult men over 40 for the same time period. Surprisingly, smoking accounted for only 30 percent of the difference in mortality between the sexes after 1890, Crimmins said. 
   
   The uneven impact of cardiovascular illness-related deaths on men, especially during middle and early older age, raises the question of whether men and women face different heart disease risks due to inherent biological risks and/or protective factors at different points in their lives, Finch said. 
   
   "Further study could include analysis of diet and exercise activity differences between countries, deeper examination of genetics and biological vulnerability between sexes at the cell level, and the relationship of these findings to brain health at later ages," he said. 
   
   The study, "Twentieth century surge of excess adult male mortality," appears in the Proceedings of the National Academy of Sciences and was supported by the National Institute on Aging. 
   
   Explore further: Women with type 1 diabetes at significantly higher risk of dying compared with men 
   
   More information: Twentieth century surge of excess adult male mortality, www.pnas.org/cgi/doi/10.1073/pnas.1421942112 
   
   ||||| Out of the 53 living supercentenarians – people over 110 years old – 51 are women. That’s more than 95 percent! In fact, you might say that no factor comes closer to predicting the likelihood of reaching such an exceptional age than simply being female. 
   
   In most mammals the two sexes age differently, and even though we’ve noticed this in our own species since the mid-18th century, researchers still haven’t been able to understand exactly why. But we do know that one of the most telltale signs of aging is the functional decline of stem cells. So perhaps it’s time to look at how stem cell behavior differs in men and women, Stanford’s Ben Dulken and Anne Brunet argue in a Cell Stem Cell paper published this week. “As the search continues for ways to ameliorate the aging process and maintain the regenerative capacity of stem cells,” they write, “let us not forget one of the most effective aging modifiers: sex.” 
   
   Adult stem cells are regulated in a sexually dimorphic manner (like flashy peacock feathers, for example), and they respond to sex hormones. By looking at the differences in regenerative decline, we might figure out how hormones like estrogen and testosterone might modify lifespan. In female mice, estrogen’s effects on stem cell populations is pretty direct: It increases the number of blood stem cells, which helps during pregnancy, and it enhances the regenerative capacity of brain stem cells at the height of estrus (that is, when she’s in heat). So far, no one’s looked into the impact these changes might have on lifespan. However, recent work with mice reveals that estrogen supplements appear to increase the lifespan of males, and a study of human eunuchs found that these men lived on average about 14 years longer than non-castrated men. 
   
   Furthermore, knocking out various genes in mice has sometimes resulted in longevity advantages for one sex but not the other. And a twin study suggested that there might be a difference in telomere length between males and females: these little caps at the ends of chromosomes help to signify the lifespans of cells. Further research is needed in order to understand how genetics might have an impact on stem cell aging in males and females and at the very least, the duo concludes, future research should emphasize the importance of controlling for sex in studies in which age is a variable. 
   
   Sex likely plays a role in defining not only lifespan but also the specific portion of a lifespan that’s healthy, or “healthspan”. The effects of sex might not necessarily be the same for the two. 
   
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target: – There's a reason we don't typically call Earth's oldest person the oldest woman in the world—the oldest person is pretty much always a woman. In fact, just two of the world's 53 living supercentenarians (people 110 and older) are men, reports IFL Science. But why is the longevity gap so stark, and how long has it been so? An international team of researchers is investigating the lifespans of men and women born between 1800 and 1935 in 13 developed nations in search of answers, reports PhysOrg, and they've found that women's superior longevity only emerged recently. Before 1840, death rates were very similar between men and women. But since those rates began to plummet in 1880 thanks in large part to improved diets, vaccinations, and better health care, female death rates have dropped 70% faster than male ones, and heart disease seems to be holding men back the most, the researchers report in Proceedings of the National Academy of Sciences. Men may be more biologically susceptible to cardiovascular health problems, and their different weight distribution could play a role here, reports Live Science. The researchers plan to further explore the differences between male and female biology, genetics, and lifestyles to look for answers. (The oldest man in the US says his trick has been to enjoy a can of beer a day.)