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.
Source: http://www.iflscience.com/health-and-medicine/why-are-almost-all-supercentenarians-women