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. 2019 Mar 9;25:1788–1799. doi: 10.12659/MSM.914621

Table 2.

Subgroup analyses for nitrite and nitrate intake and the risk of gastric cancer.

Outcomes Factor Groups Number of studies OR and 95% CI P value Heterogeneity (%) P value for heterogeneity P value between subgroups
High versus low nitrite intake Publication year 2000 or after 11 1.28 (1.09–1.51) 0.003 67.2 0.001 <0.001
Before 2000 8 1.18 (0.76–1.83) 0.462 94.5 <0.001
Study design Case-control 14 1.38 (1.02–1.85) 0.034 92.2 <0.001 0.588
Cohort 5 1.04 (0.89–1.21) 0.633 39.8 0.156
Country Europe 12 1.11 (0.87–1.43) 0.402 91.2 <0.001 <0.001
Other 7 1.56 (1.32–1.84) <0.001 22.4 0.259
Percent male ≥60.0 7 1.25 (0.78–2.02) 0.353 94.8 <0.001 <0.001
<60.0 9 1.18 (1.01–1.37) 0.032 61.2 0.008
Assessment of exposure FFQ 15 1.18 (0.94–1.48) 0.150 90.2 <0.001 <0.001
IAQ 4 1.73 (1.22–2.44) 0.002 52.7 0.096
Adjusted extent Fully 13 1.23 (0.97–1.57) 0.091 91.1 <0.001 <0.001
Partial 6 1.47 (1.20–1.79) <0.001 31.9 0.196
Study quality High 15 1.36 (1.18–1.56) <0.001 70.1 <0.001 <0.001
Low 4 0.83 (0.50–1.38) 0.466 67.6 0.026
Moderate versus low nitrite intake Publication year 2000 or after 10 1.14 (0.97–1.34) 0.104 74.1 <0.001 0.265
Before 2000 5 1.11 (0.99–1.23) 0.070 0.0 0.593
Study design Case-control 10 1.23 (1.07–1.43) 0.005 46.9 0.049 <0.001
Cohort 5 0.98 (0.88–1.10) 0.744 42.7 0.137
Country Europe 10 1.04 (0.95–1.14) 0.375 43.5 0.068 <0.001
Other 5 1.30 (1.01–1.67) 0.045 53.5 0.072
Percent male ≥60.0 4 1.43 (1.16–1.77) 0.001 0.0 0.407 <0.001
<60.0 8 0.99 (0.92–1.05) 0.672 7.1 0.376
Assessment of exposure FFQ 12 1.03 (0.95–1.12) 0.414 31.6 0.139 <0.001
IAQ 3 1.56 (1.27–1.93) <0.001 14.6 0.310
Adjusted extent Fully 11 1.11 (0.97–1.26) 0.127 69.9 <0.001 0.078
Partial 4 1.20 (1.02–1.40) 0.025 0.0 0.479
Study quality High 12 1.13 (1.00–1.27) 0.044 70.1 <0.001 0.759
Low 3 1.11 (0.76–1.61) 0.583 0.0 0.375
High versus low nitrate intake Publication year 2000 or after 8 0.89 (0.73–1.09) 0.268 61.3 0.011 <0.001
Before 2000 9 0.75 (0.60–0.93) 0.010 59.1 0.012
Study design Case-control 12 0.79 (0.63–1.01) 0.058 83.1 <0.001 0.599
Cohort 5 0.92 (0.77–1.09) 0.321 0.0 0.745
Country Europe 11 0.78 (0.64–0.95) 0.015 59.3 0.006 <0.001
Other 6 0.88 (0.65–1.21) 0.444 82.2 <0.001
Percent male ≥60.0 7 0.81 (0.61–1.08) 0.148 80.3 <0.001 0.002
<60.0 8 0.77 (0.58–1.01) 0.055 68.6 0.002
Assessment of exposure FFQ 14 0.75 (0.64–0.88) <0.001 51.3 0.014 <0.001
IAQ 3 1.10 (1.03–1.19) 0.008 0.0 0.633
Adjusted extent Fully 9 0.78 (0.61–1.02) 0.065 68.0 0.002 <0.001
Partial 8 0.85 (0.68–1.08) 0.179 74.6 <0.001
Study quality High 12 0.75 (0.63–0.89) 0.001 58.7 0.005 <0.001
Low 5 1.07 (0.94–1.23) 0.304 6.2 0.371
Moderate versus low nitrate intake Publication year 2000 or after 7 0.94 (0.84–1.05) 0.294 0.0 0.486 0.003
Before 2000 8 0.80 (0.65–0.98) 0.032 75.8 <0.001
Study design Case-control 10 0.80 (0.66–0.96) 0.018 66.8 0.001 <0.001
Cohort 5 0.96 (0.86–1.08) 0.512 0.0 0.517
Country Europe 11 0.81 (0.70–0.94) 0.006 71.2 <0.001 0.008
Other 4 1.13 (0.89–1.45) 0.324 0.0 0.671
Percent male ≥60.0 5 0.82 (0.67–1.02) 0.069 10.8 0.344 0.679
<60.0 8 0.86 (0.70–1.07) 0.170 80.2 <0.001
Assessment of exposure FFQ 13 0.85 (0.74–0.99) 0.037 69.8 <0.001 0.587
IAQ 2 0.95 (0.54–1.67) 0.853 69.2 0.072
Adjusted extent Fully 9 0.91 (0.73–1.13) 0.387 79.9 <0.001 0.883
Partial 6 0.83 (0.74–0.93) 0.002 0.0 0.632
Study quality High 11 0.86 (0.74–1.01) 0.065 73.1 <0.001 0.786
Low 4 0.85 (0.59–1.23) 0.389 49.5 0.115

CI – confidence interval; FFQ – food-frequency questionnaire; IAQ – interviewer-administered questionnaire; OR – odds ratio.