Baseline plasma level of vitamic C is associated with significantly reduced risk of cataract in the participants in the Italian–American clinical trial of nutritional supplements and age–related cataract CTNS).

Abstract

Abstract: : Purpose:CTNS is designed to evaluate the safety and efficacy of a vitamin–mineral supplement in preventing age–related cataract or delaying its progression. At the randomization visit all participants received a complete ocular examination, photographic assessment of lens status, and measurement of the plasma level of selected vitamins. We report here on the association between plasma levels of vitamins at baseline and presence and type of cataract in CTNS participants. Methods: Plasma levels of vitamin C, vitamin A, vitamin E, beta–carotene, and red blood cells glutathione reductase activity (with and without added FAD) were measured on all participants at baseline and Folate and vitamin B12 levels were also assessed on a subset (20 %) of participants. Presence and severity of N, C, and PSC opacities were assessed using lens photographs according to a modification of the Wisconsin grading system. Data on a number of variables were also collected by direct interview or measurement. We enrolled 1020 participants (55–75 yr) who, at the qualification visit, had "early cataract" (n= 710) or "no cataract" (n=310) according to study definitions. Results:Potential confounding variables that we found to be associated with cataract (age, sex, diabetes, hypertension, alcohol use, smoking, family history of cataract) together with BMI and sunlight exposure index, were included in a final multiple logistic model. We found a protective effect of high plasma levels of vitamin C on any N cataract and on any cataract. The adjusted ORs (upper vs lower quartile) were 0.56 (95% C.I. 0.35–0.91) for any cataract, and 0.47 (95% C.I. 0.27–0.80) for any N cataract. The only other nutrient–related associations of borderline significance noted in multivariate analyses were a protective effect on any cataract risk for persons in the highest quartile of glutathione–reductase activity, and on PSC cataract risk for persons in the highest vitamin A quartile. Conclusions: This study suggests that higher plasma levels of vitamin C (> 7.34 µg/ml) may be associated with a decreased risk of some types of age–related cataract. This finding may have public health implications for the prevention of this common disease.

Keywords: cataract • clinical (human) or epidemiologic studies: risk factor assessment • nutritional factors