Association between DNA repair genes (XPD and XRCC1) polymorphisms and susceptibility to age-related cataract (ARC): a meta-analysis.

BACKGROUND: DNA repair gene (XPD and XRCC1) polymorphisms have been considered as risk factors for the development of age-related cataract (ARC). To confirm the association between DNA repair gene (XPD and XRCC1) polymorphisms and the risk of ARC, a meta-analysis was conducted.
METHODS: A search was made of published literature from Institute for Scientific Information (ISI) Web of Knowledge, PubMed, Google Scholar, China National Knowledge Infrastructure (CNKI), and Wanfang Data. In addition, all studies evaluating the association between DNA repair genes (XPD and XRCC1) polymorphisms and the risk for ARC were included in our analysis. Pooled odds ratio (OR) and 95 % confidence interval (CI) were calculated by using fixed- or random-effects model. The Egger's test was used to check the publication bias.
RESULTS: Six studies on XRCC1 Arg399Gln (1,300 cases, 1,222 controls) and five studies on XPD Lys751Gln (1,092 cases, 1,061 controls) were included. For the XPD Lys751Gln (A/C) SNP, the overall analysis demonstrated that the CC genotype showed a significant association with a decreased risk for ARC compared with the AA genotype (OR = 0.59, 95 % CI, 0.38-0.92, P = 0.019). Similarly, the CC genotype showed a significant association with a decreased risk for ARC compared with the (AA + AC) genotype (OR = 0.65, 95 % CI, 0.43-0.98, P = 0.040). Subgroup analysis showed that the association between the CC genotype and decreased risk for ARC is statistically significant in Caucasians (OR = 0.41, 95 % CI, 0.24-0.73, P = 0.002) but not in Asians (OR = 1.06, 95 % CI, 0.51-2.19, P = 0.877). For the XRCC1 Arg399Gln (G/A) SNP, the overall analysis demonstrated that the A allele showed a significant association with an increased risk for ARC compared with the G allele (OR = 1.16, 95 % CI, 1.03-1.31, P = 0.015). Subgroup analyses exhibited that the association between the A allele and the risk for ARC was statistically significant in Asians (OR = 1.23, 95 % CI, 1.07-1.41, P = 0.003) but not in Caucasians (OR = 0.94, 95 % CI, 0.73-1.22, P = 0.660). Compared with the GG genotype, the GA genotype showed a significant association with an increased risk for ARC in Asians (OR = 1.32, 95 % CI, 1.08-1.61, P = 0.006) but not in Caucasians (OR = 0.58, 95 % CI, 0.27-1.26, P = 0.171). The Egger's test did not reveal an obvious publication bias among the included studies.
CONCLUSIONS: Our meta-analysis suggested that the CC genotype of XPD Lys751Gln (A/C) SNP seemed to portend a decreased risk for ARC in Caucasian populations but not in Asian populations. The A allele and GA genotype of XRCC1 Arg399Gln (G/A) SNP might increase risk for ARC in Asian populations but not in Caucasian populations. More researches with larger and more different ethnic populations on this issue are therefore necessary.