Abstract
Abstract: :
Purpose: To evaluate risk factors and protective factors for age–related macular degeneration (AMD). Methods:The U.S. Age–Related Macular Degeneration Twin Study, comprised of elderly male monozygotic (MZ) and dizygotic (DZ) twins with a mean age of 75, was designed to determine heritability and to examine genetic and environmental risk factors that may be associated with AMD. 1,2 The study population was obtained from the National Academy of Sciences–National Research Council (NAS–NRC) WWII Veteran Twin Registry. Twins were surveyed by telephone or by mail for a prior diagnosis of AMD. Study procedures included a standardized eye examination, fundus photography, blood drawing, a food frequency questionnaire and a risk factor questionnaire. Logistic regression analyses included 222 twins with AMD (intermediate or late stages) and 459 twins with no maculopathy or early signs. Results:Current smokers had a 2.1 fold increased risk (95% CI 1.1–4.0, p=0.026) of AMD while past smokers had a 1.6 fold increased risk (95% CI 1.1–2.5, p=0.021). Dietary omega–3 fatty intake was significantly associated with AMD with an odds ratio (OR) of 0.54 (95% CI 0.31–0.93) for the highest versus lowest quartile (p=0.010), and the trend for this reduction in risk of AMD was significant (p trend = 0.021). This inverse association for omega–3 intake was only apparent among subjects with low levels (below median) of linoleic acid intake, an omega–6 fatty acid, with an OR of 0.30 for the 4th quartile versus 1st quartile (CI 0.12–0.75, p trend = 0.005), whereas no significant association was seen among subjects with high linoleic acid for omega–3 fatty acid in the 4th quartile versus the 1st quartile (OR = 0.82, CI 0.37–1.84). Conclusions: This study provides further support that smoking is a consistent risk factor for AMD. Higher levels of omega–3 fatty acid intake are associated with reduced risk of AMD, particularly among subjects with low linoleic acid intake. These findings on dietary fatty acids confirm our results in two previous studies.3,4 References: 1. Invest Ophthalmol Vis Sci (1997); 3172, S676. 2. Arch. Ophthalmology (in press) 3. Arch. Ophthalmol (2001)119:1191–1199. 4. Arch. Ophthalmol (2003)121: 1728–1737.
Keywords: age-related macular degeneration • nutritional factors • clinical (human) or epidemiologic studies: risk factor assessment