Scientists have long figured out that, on average, women live longer than men. In fact, recent estimates say that, of the people who live over the age of 110, an astounding 95% - possibly even more - are women.

Even factoring in lifestyle and other variables known to influence life expectancy, i.e. smoking or drinking behavior, diet and the like, the fact of the matter is that there has to be a biological explanation for why women tend to live longer than men, scientists agree.

In a study published earlier this week, researchers Ben Dulken and Anne Brunet at Stanford University propose that the hormones estrogen and testosterone influence lifespan. Specifically, they argue that estrogen contributes to extending the life expectancy of women.
So, what's the deal with estrogen and testosterone?

For starters, this one clarification is in order: estrogen is not just one hormone. Au contraire, estrogen is actually a generic term for several compounds that, together, are traditionally considered the female hormones. As for testosterone, it is widely regarded as the male hormone.

Admittedly, estrogen is chiefly produced by the ovaries and most of the testosterone in the male body comes from the testes. Still, other body parts can too produce these hormones, which explains why women also carry small amounts of testosterone just as men to estrogen.
Estrogen and testosterone possibly influence longevity

In their report, Stanford University scientists Ben Dulken and Anne Brunet explain that, as shown by recent experiments carried out on laboratory mice, estrogen appears to have a direct impact on the population of stem cells in the body.

Specifically, the researchers say that, at least in mice, estrogen ups the number of blood stem cells and boosts the regenerative capabilities of brain stem cells. In not so many fancy words, it seems that estrogen hormones have a positive impact on the female body's ability to repair itself.

Further, the specialists say that, when given estrogen, male mice live longer than normal. Add to this the fact that the life expectancy of human eunuchs is an average 14 years longer than other men, and the theory seems plausible enough to at least consider.

Even so, the Stanford University researchers stress that science is yet to find bulletproof evidence that estrogen compounds do, in fact, prolong lifespan by pushing stem cells in the body into overdrive and that, at least for now, this idea is pretty much an educated guess.

“Because stem cell maintenance is important for tissue regeneration throughout life, sex-associated differences in stem cell aging may be associated with sexual dimorphism in lifespan,” the scientists write in their paper.