Sub-grouped studies | Genetic model | No.of Studies | No.Cases/No.Controls | Test of association | Test of heterogeneity | |||
---|---|---|---|---|---|---|---|---|
 |  |  |  | OR (95% CI) | P | Q | P Q | I 2 |
Overall | c2 carriers vs. wild | 21 | 4892/5995 | 1.02(0.90-1.17) | 0.68 | 31.37 | 0.05 | 36.26 |
 | c2 homozygotes vs. wild | 17 | 3920/5008 | 1.96(1.33-2.90) | <0.001 | 9.84 | 0.87 | 0 |
 | Dominant | 21 | 4892/5995 | 1.08(0.95-1.22) | 0.23 | 30.68 | 0.06 | 34.81 |
Asians | c2 carriers vs. wild | 6 | 981/1291 | 1.03(0.86-1.24) | 0.69 | 5.95 | 0.31 | 16.01 |
 | c2 homozygotes vs. wild | 6 | 981/1291 | 2.08(1.34-3.23) | <0.001 | 4.17 | 0.52 | 0 |
 | Dominant | 6 | 981/1291 | 1.12(0.94-1.33) | 0.18 | 4.76 | 0.44 | 0 |
Caucasians | c2 carriers vs. wild | 15 | 3911/4704 | 1.07(0.82-1.40) | 0.57 | 25.40 | 0.03 | 44.89 |
 | c2 homozygotes vs. wild | 11 | 2939/3717 | 1.58(0.68-3.68) | 0.28 | 5.35 | 0.86 | 0 |
 | Dominant | 15 | 3911/4704 | 1.03(0.86-1.24) | 0.49 | 25.49 | 0.03 | 45.09 |
High quality | c2 carriers vs. wild | 16 | 3914/4688 | 1.08(0.86-1.35) | 0.48 | 26.49 | 0.033 | 43.38 |
 | c2 homozygotes vs. wild | 13 | 3173/3913 | 1.81(1.13-2.89) | 0.013 | 5.76 | 0.92 | 0 |
 | Dominant | 16 | 3914/4688 | 1.11(0.90-1.37) | 0.29 | 24.09 | 0.064 | 37.74 |
Low quality | c2 carriers vs. wild | 5 | 978/1307 | 1.07(0.84-1.36) | 0.57 | 4.71 | 0.31 | 15.11 |
 | c2 homozygotes vs. wild | 4 | 747/1095 | 2.36(1.16-4.79) | 0.017 | 3.70 | 0.29 | 19.04 |
 | Dominant | 5 | 978/1307 | 1.12(0.81-1.55) | 0.46 | 6.38 | 0.17 | 37.39 |
Ever-smokers | c2 carriers vs. wild | 5 | 1173/831 | 0.62(0.34-1.12) | 0.11 | 8.67 | 0.07 | 53.88 |
 | c2 homozygotes vs. wild | 2 | 385/325 | 0.47(0.15-1.47) | 0.19 | 0.10 | 0.74 | 0 |
 | Dominant | 5 | 1173/831 | 0.61(0.33-1.11) | 0.10 | 8.93 | 0.063 | 55.19 |
Never-smokers | c2 carriers vs. wild | 4 | 549/677 | 1.40(0.93-2.11) | 0.09 | 0.44 | 0.93 | 0 |
 | c2 homozygotes vs. wild | 3 | 441/431 | 3.25(0.48-21.70) | 0.22 | 3.66 | 0.16 | 45.43 |
 | Dominant | 4 | 549/677 | 1.45(0.98-2.16) | 0.06 | 1.19 | 0.75 | 0 |
Alcohol- drinkers | c2 carriers vs. wild | 4 | 565/467 | 1.12(0.51-2.43) | 0.76 | 8.39 | 0.039 | 64.26 |
 | c2 homozygotes vs. wild | 2 | 198/296 | 1.48(0.34-6.44) | 0.59 | 0.83 | 0.36 | 0 |
 | Dominant | 4 | 565/467 | 1.11(0.53-2.29) | 0.77 | 7.58 | 0.055 | 60.43 |
Non-drinkers | c2 carriers vs. wild | 3 | 653/883 | 0.92(0.64-1.33) | 0.69 | 1.31 | 0.51 | 0 |
 | c2 homozygotes vs. wild | 2 | 443/370 | 2.22(0.93-5.30) | 0.07 | 0.004 | 0.94 | 0 |
 | Dominant | 3 | 653/883 | 1.07(0.76-1.52) | 0.67 | 1.08 | 0.58 | 0 |