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Risk factors shared between AMD and cardiovascular disease
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Two biomarkers for cardiovascular disease have been found to be independently associated with the progression of age-related macular degeneration, according to Johanna M. Seddon, MD and colleagues.
Dr. Seddon and colleagues conducted a prospective cohort study to test the hypothesis that a number of cardiovascular disease biomarkers, including C-reactive protein (CRP) and interleukin 6 (IL-6), are associated with increased risk for progression of AMD.
“We previously found an association between AMD and CRP in a cross-sectional analysis, but the prospective relationships between AMD, CRP and other cardiovascular disease markers [have been] unknown,” the authors said in a published report on their study.
The study involved 251 participants who were at least 60 years old and had some sign of nonexudative AMD and visual of acuity of 20/200 or better in at least one eye at baseline.
To assess AMD status, the authors used standardized grading of fundus photographs, and fasting blood samples were analyzed for the biomarkers. The average follow-up time was 4.6 years.
The study showed an association between both CRP and IL-6 and the incidence rates of the progression of AMD.
“We found that both CRP and IL-6, markers of systemic inflammation, were significantly and independently related to AMD after adjustment for known and potential for confounding factors,” the authors said.
Factors such as smoking and body mass index were also associated with AMD and have a significant positive association with both CRP and IL-6, according to the authors.
“Thus, these two variables meet the definition of a confounder,” they said. “However, even after adjustment for these and other factors, CRP and IL-6 were related to progression of AMD.”
The authors said they believe that this is the first prospective study to show an association between CRP and IL-6 levels and the progression from early or intermediate disease to advanced AMD.
“Our findings lend further support to the hypothesis that AMD may be partially mediated through inflammatory and immune-related mechanisms,” they said. “Reducing levels of CRP and IL-6 might have a favorable impact on the progression rate of AMD.”
The study is published in the June issue of Archives of Ophthalmology.