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MM DeAngelis, KM Egan, AM Lane, ES Gragoudas, TP Dryja, JW Miller; Extremely Discordant Sibpair Study of the Neovascular Form of Age-Related Macular Degeneration . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1842.
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Purpose:To analyze extremely discordant sibpairs to search for environmental and genetic factors that may contribute to the development of the neovascular form of age-related macular degeneration (AMD). Methods:We ascertain sibships in which one member has the neovascular form of AMD in at least one eye and an older sibling has normal maculae or, at most, only a few drusen. Disease status is confirmed by reading fundus photographs of every participant by at least two of the investigators. Clinical, dietary, and other factors are collected through interviews with the participants. Factors that are under scrutiny include gender, body weight, iris color, smoking history, multivitamin use, vitamin E use, aspirin use, alcohol consumption, and history of hypertension. The reference age for both the affected and unaffected siblings in a pair was the time of diagnosis of AMD of the affected member. The McNemar test for correlated proportions was used to assess statistical significance of possible risk factors for AMD. Blood samples are also collected for future molecular genetic approaches to search for genetic loci that may correlate with neovascular AMD. Results:So far, we have collected 42 extremely discordant sibpairs, and in 31 of these we have obtained complete epidemiological data. Of these 31 pairs, 26 had an unaffected older sibling with normal maculae and 5 had an unaffected older sibling with only a few macular drusen. Preliminary analysis of these 31 pairs revealed an association between smoking 25 or more pack-years of cigarettes and neovascular AMD, but this was only of borderline statistical significance (p = 0.013). No other statistically significant association was found. We continue to recruit sibpairs and assess additional possible risk factors. Conclusion: Our early results are in accord with previous reports that smoking cigarettes correlates with the neovascular form of AMD. Other factors did not appear to be associated with AMD; however, some associations might be missed in our currently small set of sibpairs. We believe that the extremely discordant sibpair method, which to our knowledge has not previously been utilized to study this disease, is a powerful approach for elucidating epidemiological and genetic factors that contribute to neovascular AMD.
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