British Medical Journal. UK: A common gut microbe might curb the risk
of developing multiple sclerosis—at least in women—suggests the largest
study of its kind published online in the Journal of Neurology Neurosurgery & Psychiatry. Helicobacter pylori might prove ‘hygiene hypothesis’ for multiple sclerosis.
If
confirmed in other studies, this might prove the hygiene hypothesis,
the premise of which is that childhood infections help to prime and
regulate the immune system and ward off autoimmune and allergic diseases
in later life, say the researchers.
The
prevalence of multiple sclerosis (MS) has increased worldwide, in
tandem with other autoimmune disease, but the reasons behind this rise
are unclear. Some studies have suggested a link between early childhood
infection and reduced MS risk, but they have all been small.
The
researchers therefore tested 550 people with confirmed MS and a
comparison group of 299 healthy people, matched for age and sex, for the
presence of antibodies to Helicobacter pylori. The tests were done
between 2007 and 2011.
H
pylori is usually acquired before the age of 2, and lasts for life in
the stomach, unless treated. Around half the world’s population is
infected with it, most of whom live in the developing world, where
hygiene standards and antibiotic prescribing rates tend to be lower than
they are in developed countries.
The
results showed that the prevalence of the infection was significantly
lower in those with MS than in the comparison group, but only among
women, in whom it was around 30% lower.
Furthermore,
after taking account of influential factors, such as age at diagnosis,
year of birth, and duration of symptoms, those women with MS who tested
positive for H pylori seemed to be less disabled by their condition
than those who tested negative for the infection.
The reverse was true in men, among whom a positive test result was linked to higher rates of disability.
There was no evidence of any link between the presence of the infection and relapse rate.
There’s
no obvious explanation for the gender disparity, which definitely
warrants further study, say the researchers. Rates of MS are higher in
women than they are in men, with most of the increased prevalence of MS
in recent years, occurring in women.
In
a linked editorial, Professor Jun-ichi Kira, of the Neurological
Institute at Kyushu University, Fukuoka, Japan, points out that the
lower disability scores reported by the women with MS who tested
positive for H pylori, suggests that the infection might be protective.
“Collectively,
such an inverse correlation of H pylori infection with MS in developing
countries where MS and allergic disorders have increased, may support
the ‘hygiene hypothesis,’ he writes.
“Although
why the protective effects of H pylori against MS were observed only in
women remains to be elucidated, but might explain the recent increase
in female to male ratio of MS in developed countries,” he adds.