Table 4

Meta-analysis of case–control studies for GSTP1 (ILE105VAL), CYP1A1 (ILE462VAL), and head and neck cancer

GSTP1CYP1A1
No. of studiesORa for any Val (95% CI)Test for heterogeneityEgger’s testNo. of studiesORa for any Val (95% CI)Test for heterogeneityEgger’s test
Overall91.10 (0.92–1.31)0.130.52121.48 (1.01–2.16)0.000.76
 Excluding studies11b1.32 (0.95–1.82)0.000.89
Cancer site
 Oral3c1.52 (1.05–2.20)0.630.225d1.48 (0.77–2.83)0.000.80
 Larynx5e0.94 (0.73–1.20)0.200.423f1.03 (0.65–1.62)0.290.07
Smoking status
 Never smokers
 Ever smokersg3h1.15 (0.87–1.51)0.490.86
Region
 Asia41.73 (0.93–3.23)0.000.18
 North America31.11 (0.86–1.43)0.480.5631.14 (0.41–3.21)0.010.26
 Europe41.08 (0.85–1.38)0.140.9441.10 (0.82–1.49)0.790.35
Year of publication
 1995–199951.15 (0.87–1.53)0.080.9751.18 (0.89–1.57)0.230.01
 2000–200341.02 (0.82–1.27)0.330.0761.37 (0.73–2.56)0.000.48
No. of cases and controls
 <100 cases or <100 controls31.74 (0.57–5.28)0.000.99
 ≥100 cases & 100≥controls81.06 (0.90–1.24)0.240.6881.20 (0.88–1.63)0.040.88
Control source
 Hospital-healthy or population40.98 (0.70–1.17)0.070.3671.43 (0.96–2.12)0.010.74
 Hospital51.21 (1.01–1.45)0.650.5641.12 (0.58–2.13)0.020.99
Matching
 Individual/frequency matching31.12 (0.89–1.42)0.470.6051.84 (0.98–3.46)0.020.72
 No matching41.18 (0.90–1.55)0.120.9061.09 (0.79–1.50)0.050.14