According to a report in the October issue of Archives of Ophthalmology, one of the JAMA/Archives journals, high blood levels of C-reactive protein, a substance associated with inflammation, is related to an increased risk for age-related macular degeneration.
Age-related macular degeneration or aging macula disorder (AMD) occurs when the macula, the area at the back of the retina involved in sharp vision, deteriorates over time. Inflammation appears to play a role in the development of AMD, according to background information in the article. Proteins associated with inflammation, such as fibrinogen and C-reactive protein, have been found in drusen—the white deposits below the retina that are a hallmark of AMD.
Sharmila S. Boekhoorn, M.D., Ph.D., of the Erasmus Medical Center, Rotterdam, the Netherlands, and colleagues examined C-reactive protein levels in 4,914 individuals at risk for AMD. At the initial examination, conducted between 1990 and 1993, blood samples were collected and photographs were taken of the retina. Three additional examinations were conducted over an average of 7.7 years.
During this time, 658 individuals were diagnosed with AMD, including 561 with early (initial stage) AMD and 97 with late (more advanced) AMD. As an individual's C-reactive protein level increased above the median (midpoint) of the study population, he or she became more likely to develop AMD.
"Evidence is accumulating that inflammatory and immune-associated pathways have a role in other degenerative diseases associated with advancing age, such as atherosclerosis and Alzheimer's disease," the authors write. "Drusen components have been found in atherosclerotic plaques and deposits in Alzheimer's disease, and AMD, atherosclerosis, and Alzheimer's disease may partly share a similar inflammatory pathogenesis."
Based on these results, reducing C-reactive protein levels could potentially decrease risk for AMD, the authors note. "A substance that can selectively inhibit C-reactive protein synthesis has not yet been developed, to our knowledge," they write. "Smoking and high body mass index increase C-reactive protein levels. Moderate alcohol intake, diets with a low glycemic index and statin and multivitamin use reduce C-reactive protein levels." Smoking and obesity are already known to increase risk for AMD.