BMJ: Recent gut and urinary tract infections may curb risk of
rheumatoid arthritis. Explanation could lie in subsequent changes in gut bacteria,
say researchers.
Recent gut and urinary tract infections may curb the risk of
developing rheumatoid arthritis, suggests research published
online in the
Ann
als of the Rheumatic Diseases.
One possible explanation could lie in the way in which these
infections alter the types of bacteria resident in the gut
(microbiome), say the researchers.
They set out to look at the impact of different types of infection
o
n the risk of developing rheumatoid arthritis in almost 6500
people living in south and central Sweden.
Some 2831 of the entire sample had been newly diagnosed
with rheumatoid arthritis between 1996 and 2009. The
remaining 3570, who were randomly selected
from the
population, were healthy, but matched for age, sex, and area of
residence with the patients.
All participants were asked whether they had had any gut,
urinary tract, or genital infections in the preceding two
years.
They were also asked if they
had had prostatitis (inflamed
prostate), or antibiotic treatment for sinusitis, tonsillitis/other
throat infection, or pneumonia during this time.
The average age of all participants at study entry was 52, and 7
out of 10 of them were women.
Gut, urinary tract, and genital infections within the preceding
two years were each associated with a significantly lowered risk
of developingrheumatoid arthritis: by 29%, 22%, and 20%,
respectively.
And having all three types of infection in the preceding two
years
was linked to a 50% lower risk, after taking account of
influential factors.
By contrast, no such associations were found for recent
respiratory infections and pneumonia.
Factoring in smoking and socioeconomic background made no
difference to the overal
l findings.
More recent infection within the past year did not affect
rheumatoid arthritis risk, but the impact of gut, urinary tract, and
genital infectionswithin the past two years seemed to be
stronger in those who had tested positive for a particular
type of
protein associated with subsequent development of rheumatoid
arthritis (ACPA).
This is an observational study so no definitive conclusions can
be drawn about cause and effect.
But the researchers say their findings “are particularly
interesting i
n light of emerging data implicating that the
microbiome in the gut mayplay a role in rheumatoid arthritis
pathogenesis.”
This might be because the linings of the gut are exposed to a
high load of bacterial antigens, which may either initiate or
modify i
nflammation, and so could possibly influence the risk of
developing the disease, explain the researchers.
In support of their findings, they point out that the infection sites
identified in their study are primarily infected with gram negative
bacteria, a
nd antibiotics used to treat these bacteria have
proved effective for treating rheumatoid arthritis.