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Common
Bug May Up Risk of Age-Related Vision Loss Reuters
Health, April 22, 2003 NEW
YORK (Reuters Health) - New findings suggest that a frequent cause of
age-related vision impairment may be linked to a common bacterial
infection. U.S.
researchers discovered that people with age-related macular degeneration
(AMD) tended to carry higher levels of antibodies targeted against the
bacterium Chlamydia pneumoniae than those without AMD. Such targeted
antibodies are a sign of past infection. Although
the reason for this relationship is not yet clear, the findings suggest
that infection with C. pneumoniae may cause changes in the body that
increase a person's risk of developing AMD, according to the study
authors. They
report the results in the April issue of the Archives of Ophthalmology. AMD
occurs when light-sensitive cells in the macula, the tissue at the center
of the retina, break down. This can make it difficult to read, drive or
perform other activities that require fine vision. An
estimated one-third of Americans age 75 and older have AMD. C.
pneumoniae normally infects the respiratory system, but it's also
suspected of promoting certain chronic illnesses. Research has shown that
infection with the bug may promote heart disease by producing inflammation
in blood vessels. Some experts believe that this inflammation could damage
the blood vessel lining and potentially contribute to artery blockages. In
addition, this inflammation could disturb unstable artery blockages and
help trigger a heart attack or stroke. As
evidence for a role of C. pneumoniae in blood vessel disease, researchers
have found that people with the artery-clogging disease atherosclerosis
have higher levels of antibodies against the bacterium than people without
the condition. In
addition, there's evidence that AMD and atherosclerosis share some risk
factors, including smoking and high blood pressure. And some researchers
suspect that chronic inflammation may contribute to AMD. During
the current study, Dr. Murat V. Kalayoglu of the Massachusetts Eye and Ear
Infirmary in Boston and colleagues examined blood samples from 43 visitors
to a VA hospital eye clinic, 25 of whom had AMD. According
to the researchers, "patients with (AMD) were more likely to have
higher levels of anti-C. pneumoniae antibodies compared with patients
without (AMD)." This
association remained after the researchers accounted for patients' age and
smoking habits. In
contrast, antibodies against two other bugs the researchers tested
appeared no more often in the blood of people with AMD. Kalayoglu
and colleagues suggest that C. pneumoniae may increase the risk of AMD by
directly infecting eye tissues or increasing the production of substances
that promote inflammation. They
caution, however, that the people included in the study were mostly male
and had several other illnesses -- suggesting that the same results may
not apply to the general population. Given
the potential role of C. pneumoniae in cardiovascular problems,
investigators are currently studying whether bacteria-fighting antibiotics
could help treat artery disease. Kalayoglu and the Massachusetts Eye and Ear Infirmary have a proprietary interest in some of the study data, according to the report. Copyright
© 2002 Global Action on Aging
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