title: Relations of serum ascorbic acid and alpha-tocopherol to diabetic retinopathy in the Third National Health and Nutrition Examination Survey.
abstract: The protective relation of ascorbic acid and alpha-tocopherol to the development of diabetic retinopathy has not been thoroughly evaluated in epidemiologic studies. The association of prevalent diabetic retinopathy with serum ascorbic acid and alpha-tocopherol was studied among participants with type 2 diabetes (>or=40 years) (n = 998) in the Third National Health and Nutrition Examination Survey (1988-1994); 20% of the sample (n = 199) had prevalent retinopathy. The overall odds ratio for retinopathy among participants in quartile 4 compared with quartile 1 for serum ascorbic acid was 1.3 (95% confidence interval: 0.8, 2.3), with a p for trend = 0.60 after adjustment for the confounders of smoking, race, waist/hip ratio, hypertension, and duration of diabetes. The overall odds ratio for retinopathy among participants in quartile 4 compared with quartile 1 for serum alpha-tocopherol was 2.7 (95% confidence interval: 1.6, 4.6), with a p for trend = 0.14 after adjustment for confounders. After removal of supplement users of vitamin C (n = 307) or vitamin E (n = 298), the odds ratio changed direction or was attenuated: adjusted odds ratios for retinopathy among participants in quartile 4 compared with quartile 1 for serum ascorbic acid and alpha-tocopherol = 0.7 (95% confidence interval: 0.3, 1.4) and 1.6 (95% confidence interval: 0.9, 2.9), respectively. In summary, no significant associations were observed between serum levels of major dietary antioxidants and retinopathy. Recent use of supplements for treatment of complications of diabetes may explain the direct associations.
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of Wisconsin Medical School, Madison 53705-2397, USA.
authors.forename: Amy E
authors.initials: AE
authors.lastname: Millen
authors.forename: Michael
authors.initials: M
authors.lastname: Gruber
authors.forename: Ron
authors.initials: R
authors.lastname: Klein
authors.forename: Barbara E K
authors.initials: BE
authors.lastname: Klein
authors.forename: Mari
authors.initials: M
authors.lastname: Palta
authors.forename: Julie A
authors.initials: JA
authors.lastname: Mares
mesh_terms: D000328:Adult; D000368:Aged; D001205:Ascorbic Acid / Q000097:blood*; D003924:Diabetes Mellitus, Type 2 / Q000150:complications*; D003930:Diabetic Retinopathy / Q000453:epidemiology* / Q000517:prevention & control*; D019587:Dietary Supplements; D016021:Epidemiologic Studies; D005260:Female; D006306:Health Surveys; D006801:Humans; D008297:Male; D008875:Middle Aged; D009749:Nutrition Surveys; D016017:Odds Ratio; D015995:Prevalence; D024502:alpha-Tocopherol / Q000097:blood*
chemical_list: D024502:alpha-Tocopherol; D001205:Ascorbic Acid