Largest twin study of age-related macular degeneration finds genetics and environment play large role in disease

Researchers led by Johanna M. Seddon, M.D., at the Massachusetts Eye and Ear Infirmary, Harvard Medical School and Harvard School of Public Health conducted the largest study of twins of its kind. Analyses of twins showed that genetic factors play a substantial role in the etiology of AMD and associated macular characteristics, explaining 46 percent to 71 percent of the variation in the overall severity of the disease. They found that environmental factors unique to each twin also contribute to the occurrence of this disease.

Johanna M. Seddon, M.D., Sc.M., director of the Epidemiology Unit at the Massachusetts Eye and Ear Infirmary and associate professor of ophthalmology at Harvard Medical School, and her colleagues enrolled 840 twins throughout the United States who all had a complete ocular examination and photographs of the macula. Of these twins, 331 had no signs of maculopathy and 241 had early signs, while 162 had intermediate AMD and 106 had advanced AMD.

This is the largest twin study of AMD to date and the only population-based twin registry in the United States among elderly individuals. Authors quantified substantial genetic influences on AMD, contributed new information about the heritability of AMD, and established an important environmental contribution. “This twin study underscores the need for a multifactorial approach that incorporates genetic, environmental and biological factors to study the pathogenesis and clinical management of this blinding disease,” said Seddon.