1 August 2020 | New Scientist | 45That’s a down side of having two
X chromosomes?
Yes, but there’s also an advantage of
having a somewhat autoreactive immune
system. Many microbes invade and escape
detection in the body because they
resemble human cells. Females have a
better ability to be able to discern this kind
of wolf in sheep’s clothing because they
keep cells that are more likely to attack
things that resemble themselves. So women
have higher rates of autoimmune diseases,
like rheumatoid arthritis, lupus, multiple
sclerosis. But if it helps you survive covid-19,
that’s the benefit.
Are there any other benefits to a stronger
immune system?
More work is needed on this, but perhaps
the propensity to autoimmunity is one
of the explanations for females having
a lower chance of certain cancers.
Malignancies begin with our own healthy
cells. The possible benefit of having an
immune system that’s more geared to
attack your own cells is that you are
clearing pre-malignant cells before
they are detectable medically.
Couldn’t that difference also be due to
behavioural reasons, like men smoking
and drinking more?
Yes, but I believe that that pattern holds
true for certain cancers that start before
puberty. The major differences in behaviour
begin after puberty. But, there’s no way to
know for sure.If these differences between the sexes are
so widespread, why haven’t we heard of
them before?
When you see a six-foot-four man who is an
Olympic weight-lifter and you try to say that
they don’t have a survival advantage over a
five-foot-three woman, it’s difficult to
understand the difference between biological
strength and physical strength. Plus, there’s
resistance to any new paradigm. The current
paradigm is that most of the health
differences that we are seeing between men
and women are behavioural; it’s very hard for
people to let go of behaviour.
My lightbulb moment was in a neonatal
intensive care unit. Although I was taught
that the difference between the sexes was
behaviourally based, I was seeing that it
seemed to be driven by biology.Why does it matter?
Because we need to understand the basis for
the biological differences between men and
women, in terms of disease susceptibility and
sensitivity to medications. In general, drugs
are metabolised slower in women, and their
gut transit time is slower so women have to
wait longer after eating to have an empty
stomach. But if people go to their physicians,
sex is never considered as a dosing variable
and there is no requirement for drug
approvals to recognise sex-based differences.
Melanoma kills twice as many young men
as women. It’s a classic example of where we
blame men for behaviour: using less sun
screen, not going to their doctor. Yet the
differences in melanoma risk are actually
biological. Women are more protected thanks
to stronger immune response and benefits
from female sex hormones. We should be
investing in screening for men at a much
earlier age. We need to stop treating men and
women as if they are biologically the same. ❚Clare Wilson is a biomedical reporter
at New Scientist and author of Health
Check: newscientist.com/healthcheck.
Follow her @ClareWilsonMedJILLLEHMANN^ PHOTOGRAP
HY
/GETT
Y^ IMAGES“ It’s hard to argue
that the sexes’
behaviour is
different in the
incubator”