Methods: Literature searches, quality scores for the studies, and inter-rater evaluation on data coding was completed to ensure data accuracy for pooled meta-analyses.
Results: Preliminary analyses included 31,146 LC cases and 38,736 controls from 122 studies. The MPO gene mutations (GA and AA subtypes) in Asians were lower (16.7-33.3%) than Caucasians (31.8-49.1%) across the world, for control and case groups. However, the GSTM1 gene mutation variation (null subtype) was highest in Italians (87.5%) than other populations. Pollution indicators were checked and shown worse in Asia than other countries. For lifestyle related meta-analyses, smoking was associated with an increased risk of LC (98 studies, 28,831 cases, 35,069 controls, RR=1.40, p < 0.0001). Low vegetable intakes were associated with increased LC risk (RR = 1.26, P < 0.05) in 7 studies. No second hand smoking (6 studies) and limiting indoor pollution (3 studies) were protective for LC (RR=0.73 and 0.77, both P<0.05).
Conclusion: For association of GSTM1 gene variations, genotype present (44.3% cases, 47.9% controls) was protective against LC for all populations combined in the world (RR = 0.94, p < 0.0001). Future studies are needed to examine epigenetic factors for population health associated with MPO and GSTM1 gene variations in the prevention of LC.