Last month, I attended ‘MS At the
Limits’, and the final talk by Dr Riley Bove (University of California, San
Francisco) was truly fascinating. I know I am a bit delayed in posting this but
I thought I would share some of the key points…
As most of us know, MS affects
more women than men, but you might not know that women tend to have more
relapses and that the ratio of men:women affected by MS is on the rise. The most
obvious culprit here is hormones, but it is also possible that the higher
prevalence/relapse rate in women is related to nutrition or behaviour. For
example, women tend to attend the doctors far more frequently than men, so are
they more likely to report relapses or symptoms?
When we look at the lifetime of
humans, we are very unique in that we are the only species to have a period of
puberty and a period of post-fertility
(primates are the only other species to have a period of adolescence, and only two
species of whale live post-menopause). These life phases are very much dictated
by hormones, could it be coincidence that we are the only species to go through
all these hormonal changes and the only species to develop MS?
Early puberty is a risk factor
for women developing MS, and the earlier puberty occurs, the earlier they tend
to develop MS. So surely, this is direct evidence of a hormonal cause? However,
it could be that puberty and MS have common risk factors, such as genetic
mutations or BMI (increased weight is associated with both increased risk of MS
and earlier onset of puberty). Also, if hormones are the main culprit here, you
would expect a correlation between disease onset/progression and oral
contraceptives wouldn’t you? But studies so far suggest only a slight effect.
However, the more we look, the
more links we see to hormonal influence, although most findings show weak
correlations or slight effects.
Later age at birth of the first
child may be linked with MS onset. So, having children earlier in life appears
to be protective. Pregnancy also has a short-term protective effect, reducing
relapses but increasing risk of relapse in the short-term, after birth. Breast-feeding
appears to be protective, so may help reduce the short-term increased risk of
relapse post-birth.
As for the menopause and MS, EDSS
scores appear to progress faster post-menopause. Also, early menopause through
surgery is linked with increased cognitive decline and dementia (not yet
studies in pwMS specifically). Could this be linked to hormone replacement therapy
(HRT), which women take after surgical menopause? Further studies are required to
find out.
Let’s not forget about the men… lower testosterone in men has been found to
correlate with higher EDSS scores in early MS, suggesting a faster rate of
disease progression in early disease. So, could testosterone be protective in
MS? Several studies have shown that it might be, but little attention has been
paid to this topic in recent years.
So, can we blame hormones for the
higher incidence of MS in women? Possibly, but proceed with caution!