Abstract
ObjectiveTo examine the association between vitamin C and cataract in the Indian setting.DesignPopulation-based cross-sectional analytic study.ParticipantsA total of 5638 people aged ≥60 years.MethodsEnumeration of randomly sampled villages in 2 areas of north and south India to identify people aged ≥60 years. Participants were interviewed for socioeconomic and lifestyle factors (tobacco, alcohol, household cooking fuel, work, and diet); attended a clinical examination, including lens photography; and provided a blood sample for antioxidant analysis. Plasma vitamin C was measured using an enzyme-based assay in plasma stabilized with metaphosphoric acid, and other antioxidants were measured by reverse-phase high-pressure liquid chromatography.Main Outcome MeasuresCataract and type of cataract were graded from digital lens images using the Lens Opacity Classification System III (LOCS III), and cataract was classified from the grade in the worse eye of ≥4 for nuclear cataract, ≥3 for cortical cataract, and ≥2 for posterior subcapsular cataract (PSC). Any cataract was defined as any unoperated or operated cataract.ResultsOf 7518 enumerated people, 5638 (75%) provided data on vitamin C, antioxidants, and potential confounders. Vitamin C was inversely associated with cataract (adjusted odds ratio [OR] for highest to lowest quartile = 0.61; 95% confidence interval (CI), 0.51–0.74; P=1.1×10−6). Inclusion of other antioxidants in the model (lutein, zeaxanthin, retinol, β-carotene, and α-tocopherol) made only a small attenuation to the result (OR 0.68; 95% CI, 0.57–0.82; P < 0.0001). Similar results were seen with vitamin C by type of cataract: nuclear cataract (adjusted OR 0.66; CI, 0.54–0.80; P < 0.0001), cortical cataract (adjusted OR 0.70; CI, 0.54–0.90; P < 0.002), and PSC (adjusted OR 0.58; CI, 0.45–0.74; P < 0.00003). Lutein, zeaxanthin, and retinol were significantly inversely associated with cataract, but the associations were weaker and not consistently observed by type of cataract. Inverse associations were also observed for dietary vitamin C and cataract.ConclusionsWe found a strong association with vitamin C and cataract in a vitamin C–depleted population.Financial Disclosure(s)The author(s) have no proprietary or commercial interest in any materials discussed in this article.
Highlights
The study complied with the guidelines in the Declaration of Helsinki, and ethics approval was received from the Indian Council for Medical Research (ICMR), Research Ethics Committees of the All India Institute of Medical
Plasma vitamin C was available in 5638 people (2668 samples from the Dr Rajendra Prasad Center for Ophthalmic Sciences and 2970 from the Aravind Eye Hospital Pondicherry)
Of the participants who attended the eye examination, there were no significant differences by age (Pϭ0.1), sex (Pϭ0.4), or cataract status (Pϭ0.6) for those with vitamin C measurements compared with those without
Summary
India accounts for approximately 20% of the global burden of blindness, with cataracts being the principal cause.[1] Populationbased studies have reported high prevalence rates of cataract in India[2,3,4] compared with western populations, even when the level of cataract surgery is taken into account. Environmental, nutritional, and genetic factors may be important explanatory factors of these high rates, but to date, there is limited information on these in the Indian setting, on antioxidants (especially vitamin C) considered to play a key role in protecting the lens from oxidative stress.[5] In a small feasibility study for the current study, we reported inverse associations between cataract and plasma levels of vitamin C and other antioxidants.[6] The levels of vitamin C in the feasibility study were lower than observed in high-income countries. Our overall objectives were to examine the prevalence and risk factors for cataract and to investigate vitamin C and cataract
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