Table 1. Subgroup analyses of dairy product and calcium intakes and lung cancer risk, high vs low intake.
| Subgroups | N | RR (95% CI) | Heterogeneity |
P-heterogeneity | P-interaction | |||
|---|---|---|---|---|---|---|---|---|
| P value | Q statistic | I2 | ||||||
| Total dairy |
13 | 1.05 (0.84–1.31) | 0.67 | 44.67 | 73.10% | <0.01 | ||
| Design | Case-control | 9 | 1.24 (0.91–1.70) | 0.17 | 28.47 | 71.90% | <0.01 | |
| Cohort | 4 | 0.75 (0.52–1.08) | 0.12 | 44.67 | 70.20% | 0.018 | 0.07 | |
| Ethnicity | America | 8 | 1.17 (0.86–1.61) | 0.32 | 37.14 | 81.20% | <0.01 | |
| Europe | 4 | 0.81 (0.64–1.03) | 0.14 | 3.77 | 20.40% | 0.29 | 0.41 | |
| Outcome | Incidence | 10 | 1.20 (0.94–1.52) | 0.14 | 33.04 | 72.80% | <0.01 | |
| Mortality | 3 | 0.62 (0.45–0.84) | <0.01 | 1.43 | 0.00% | 0.489 | 0.04 | |
| Quality | Low | 6 | 1.30 (0.83–2.05) | 0.26 | 24.60 | 79.70% | <0.01 | |
| High | 7 | 0.89 (0.71–1.10) | 0.28 | 12.35 | 51.40% | 0.06 | 0.14 | |
| Sex | Male | 5 | 1.46 (0.95–2.25) | 0.08 | 24.46 | 83.60% | <0.01 | |
| Female | 6 | 0.92 (0.82–1.02) | 0.13 | 4.23 | 0.00% | 0.52 | 0.37 | |
| No. of cases | ≤300 | 0.88 (0.66–1.18) | 0.39 | 11.06 | 45.70% | 0.09 | ||
| >300 | 1.23 (0.87–1.74) | 0.23 | 31.48 | 84.10% | <0.01 | 0.22 | ||
| Smoking† | Smokers | 4 | 1.32 (0.65–2.68) | 0.44 | 21.90 | 86.30% | <0.01 | |
| Non-smokers | 4 | 1.55 (0.98–2.45) | 0.06 | 4.75 | 36.80% | 0.19 | 0.93 | |
| Adjustment for confounders | ||||||||
| Smoking | Yes | 11 | 1.09 (0.86–1.39) | 0.46 | 42.00 | 76.20% | <0.01 | |
| No | 2 | 0.77 (0.51–1.16) | 0.22 | 0.93 | 0.00% | 0.34 | 0.44 | |
| Energy intake | Yes | 6 | 1.16 (0.85–1.60) | 0.34 | 20.11 | 75.10% | <0.01 | |
| No | 7 | 0.95 (0.65–1.40) | 0.80 | 23.83 | 74.80% | <0.01 | 0.45 | |
| Milk | 22 | 1.08 (0.80–1.46) | 0.61 | 220.15 | 90.50% | <0.01 | ||
| Design | case-control | 15 | 1.15 (0.77–1.71) | 0.50 | 212.73 | 93.40% | <0.01 | |
| Cohort | 7 | 0.90 (0.74–1.09) | 0.28 | 5.64 | 0.00% | 0.46 | 0.55 | |
| Location | America | 8 | 1.43 (1.03–1.97) | 0.03 | 20.46 | 65.80% | <0.01 | |
| Europe | 9 | 0.87 (0.63–1.21) | 0.87 | 135.07 | 97.00% | <0.01 | ||
| Asia | 5 | 1.08 (0.44–2.65) | 0.40 | 36.61 | 78.20% | <0.01 | 0.47 | |
| Outcome | Incidence | 18 | 1.16 (0.81–1.67) | 0.41 | 214.78 | 92.10% | <0.01 | |
| Mortality | 4 | 0.81 (0.65–1.02) | 0.08 | 1.22 | 0.00% | <0.01 | 0.32 | |
| Quality | Low | 13 | 1.08 (0.80–1.46) | 0.56 | 210.79 | 94.30% | <0.01 | |
| High | 9 | 0.94 (0.80–1.12) | 0.54 | 8.45 | 5.40% | 0.39 | 0.61 | |
| Sex | Male | 6 | 1.76 (0.78–3.97) | 0.18 | 143.22 | 96.50% | <0.01 | |
| Female | 10 | 0.94 (0.73–1.22) | 0.65 | 25.06 | 64.10% | <0.01 | 0.13 | |
| No. of cases | ≤300 | 11 | 1.09 (0.62–1.92) | 0.77 | 110.98 | 91.00% | <0.01 | |
| >300 | 11 | 1.07 (0.75–1.53) | 0.69 | 105.74 | 90.50% | <0.01 | 0.99 | |
| Adjustment for confounders | ||||||||
| Smoking | Yes | 15 | 1.35 (0.90–2.01) | 0.14 | 163.60 | 91.40% | <0.01 | |
| No | 7 | 0.67 (0.57–0.79) | <0.01 | 6.84 | 12.30% | 0.34 | 0.03 | |
| Energy intake | Yes | 5 | 1.21 (0.75–1.94) | 0.79 | 193.11 | 91.70% | <0.01 | |
| No | 17 | 1.05 (0.73–1.51) | 0.44 | 20.83 | 80.80% | <0.01 | 0.72 | |
| Cheese | 10 | 0.83 (0.62–1.12) | 0.23 | 31.04 | 71.00% | |||
| Design | Case-control | 8 | 0.90 (0.62–1.30) | 0.58 | 28.59 | 75.50% | <0.01 | |
| Cohort | 2 | 0.63 (0.46–0.87) | <0.01 | 0.03 | 0.00% | 0.87 | 0.38 | |
| Location | America | 4 | 0.84 (0.64–1.12) | 0.24 | 3.26 | 8.10% | 0.35 | |
| Europe | 5 | 0.94 (0.52–1.72) | 0.85 | 26.22 | 84.70% | <0.01 | ||
| Asia | 1 | 0.64 (0.44–0.93) | 0.02 | / | / | / | 0.49 | |
| Outcome | Incidence | 8 | 0.90 (0.62–1.31) | 0.58 | 28.67 | 75.60% | <0.01 | |
| Mortality | 2 | 0.63 (0.46–0.87) | <0.01 | 0.03 | 00.00% | 0.87 | 0.38 | |
| Quality | Low | 6 | 0.78 (0.52–1.19) | 0.25 | 20.83 | 76.00% | <0.01 | |
| High | 4 | 0.92 (0.56–1.50) | 0.73 | 9.67 | 69.00% | 0.02 | 0.67 | |
| No. of cases | ≤300 | 5 | 0.75 (0.41–1.37) | 0.35 | 20.53 | 80.50% | <0.01 | |
| >300 | 5 | 0.89 (0.66–1.21) | 0.47 | 9.53 | 58.00% | 0.05 | 0.52 | |
| Adjustment for confounders | ||||||||
| Smoking | Yes | 7 | 1.01 (0.74–1.38) | 0.93 | 14.49 | 58.60% | 0.03 | |
| No | 3 | 0.53 (0.33–0.85) | <0.01 | 5.75 | 65.20% | 0.06 | 0.05 | |
| Energy intake | Yes | 2 | 0.80 (0.54–1.19) | 0.27 | 0.99 | 0.00% | <0.01 | |
| No | 8 | 0.85 (0.59–1.23) | 0.39 | 30.17 | 76.80% | 0.32 | 0.26 | |
| Yogurt | 5 | 0.88 (0.62–1.25) | 0.48 | 9.93 | 59.70% | 0.04 | ||
| low-fat milk | 3 | 0.98 (0.69–1.41) | 0.93 | 1.68 | 0.00% | 0.43 | ||
| Calcium | ||||||||
| Total | 3 | 0.99 (0.70–1.38) | 0.94 | 8.00 | 75.00% | 0.02 | ||
| Dietary | 5 | 0.85 (0.63–1.13) | 0.26 | 26.87 | 81.40% | <0.01 | / | |
Note: For subgroup analysis stratified by smoking status, the data on the categories of dairy and milk intakes were both included, since only a small number of original studies reported the results, the forest plot was shown in Supplementary Fig. S1.