RT Journal Article
SR Electronic
T1 Genetic variants in a sodium-dependent vitamin C transporter gene and age-related cataract
JF British Journal of Ophthalmology
JO Br J Ophthalmol
FD BMJ Publishing Group Ltd.
SP 1223
OP 1227
DO 10.1136/bjophthalmol-2018-312257
VO 103
IS 9
A1 Ravilla D Ravindran
A1 Periasamy Sundaresan
A1 Tiruvengada Krishnan
A1 Praveen Vashist
A1 Giovanni Maraini
A1 Vijayan Saravanan
A1 Usha Chakravarthy
A1 Liam Smeeth
A1 Dorothea Nitsch
A1 Ian S Young
A1 Astrid E Fletcher
YR 2019
UL http://bjo.bmj.com/content/103/9/1223.abstract
AB Background Cataract is a major health burden in many countries and a significant problem in India. While observational studies show lower cataract risk with increasing dietary or plasma vitamin C, randomised controlled trials of supplements have been negative. Genetic variants in vitamin C transporter proteins (SLC23A1), especially rs33972313, may provide evidence on a causal association of vitamin C with cataract.Methods We used data from a randomly selected population-based study in people aged 60 years and above in north and south India. Of 7518 sampled, 5428 (72%) were interviewed for socioeconomic and lifestyle factors, attended hospital for lens imaging and blood collection and were subsequently genotyped for rs33972313 and rs6596473. Mixed or pure types of cataract were graded by the Lens Opacity Classification System III as nuclear (2404), cortical (494) or posterior subcapsular cataract (PSC) (1026); 1462 had no significant cataract and no history of cataract surgery and 775 had bilateral aphakia/pseudophakia.Results rs33972313 was associated with cortical (OR 2.16; 95% CI 1.34 to 3.49, p=0.002) and PSC (OR 1.68; 95% CI 1.06 to 2.65, p=0.03) but not with nuclear cataract. In analyses of pure cataracts, associations were found only between rs33972313 and pure cortical cataracts (OR 2.29; 95% CI 1.12 to 4.65, p=0.03) and with a standardised cortical opacity score. There was no association with rs6596473 and any cataract outcomes.Conclusions Using an established genetic variant as a proxy for lifetime ascorbate concentrations, our results support a causal association of vitamin C with cataract.