Researchers at the Massachusetts Eye and Ear Infirmary and Department of Biostatistics at Harvard Medical School studied 681 male twins from the National Academy of Sciences-National Research Council World War II Veteran Twin Registry. To determine genetic and environmental risk factors for Age-related Macular Degeneration (AMD), twins were surveyed for a prior diagnosis of AMD and underwent an eye examination, fundus photography, and food frequency and risk factor questionnaires. The study included 222 twins with intermediate and late-stage AMD and 459 twins with no signs of the disease.
"Current smokers had a 1.9-fold increased risk of developing AMD, while past smokers had about a 1.7-fold increased risk," said Johanna M. Seddon, M.D., director of the Epidemiology Unit at the Massachusetts Eye and Ear Infirmary and an associate professor of ophthalmology at Harvard Medical School. "We also found that increased intake of fish reduced the risk of AMD, particularly if they ate two more servings per week. Dietary omega-3 fatty intake was also inversely associated with AMD. This study of twins provides further evidence that cigarette smoking increases risk while fish consumption and omega-3 fatty acid intake reduce risk of AMD."
AMD is the leading cause of irreversible visual impairment and blindness among persons aged 60 and older. With the elderly population steadily growing, the burden related to this loss of visual function will increase. Limited treatment options exist and prevention remains the best approach for addressing this public health concern.
Lead author Dr. Seddon and her colleagues previously reported that the heritability of AMD is high (46% to 71%) in this same cohort of twins (Arch Ophthalmol 2005). They also found that systemic markers of inflammation, including serum levels of high sensitivity C-reactive protein, as well as plasma homocysteine are associated with AMD (JAMA 2004, Am J Ophthalmol 2006). A decade ago they reported the increased risk of AMD with cigarette smoking (JAMA 1996), and the decreased risk of this disease related to dietary intake of carotenoids and foods rich in lutein and zeaxanthin (JAMA 1994). They also found in several of their study cohorts that fish intake appears beneficial and reduces risk of AMD (Arch Ophthalmol 2001, 2003, and current article), and high body mass index or obesity is also a risk factor for progression of the disease. (Arch Ophthalmol 2003).
This most recent research was funded by grants from the National Institute of Health, the Foundation Fighting Blindness Inc., the Retirement Research Foundation, DSM Inc, the Massachusetts Lions Eye Research Fund, and the Epidemiology Research Fund.
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