Table 2.
Subgroup analyses of OC use and kidney cancer risk
| Subgroup | Ever use | Long-term use | ||||||
|---|---|---|---|---|---|---|---|---|
|
| ||||||||
| N | RR (95% CI)a | I2 (%) | P-heterogeneity | N | RR (95% CI)a | I2 (%) | P-heterogeneity | |
| Total studies | 12 | 0.89 (0.82-0.98) | 0.0 | 0.707 | 9 | 0.80 (0.68-0.94) | 24.4 | 0.226 |
| Designs | ||||||||
| Case-control | 7 | 0.88 (0.75-1.02) | 0.0 | 0.451 | 5 | 0.76 (0.46-1.25) | 56.3 | 0.058 |
| Cohort | 5 | 0.90 (0.81-1.01) | 0.0 | 0.697 | 4 | 0.80 (0.66-0.97) | 0.0 | 0.697 |
| Geographic locations | ||||||||
| North America | 8 | 0.93 (0.84-1.02) | 0.0 | 0.783 | 7 | 0.83 (0.70-0.99) | 20.6 | 0.272 |
| Europe | 2 | 0.95 (0.58-1.55) | 0.0 | 0.968 | 1 | 0.80 (0.30-2.2) | NA | NA |
| Oceania | 1 | 0.70 (0.40-1.10) | NA | NA | - | - | - | - |
| Publication year | ||||||||
| Before 2000 | 5 | 0.80 (0.66-0.97) | 0.0 | 0.585 | 4 | 0.68 (0.36-1.25) | 61.3 | 0.052 |
| After 2000 | 7 | 0.92 (0.83-1.03) | 0.0 | 0.738 | 5 | 0.82 (0.68-0.98) | 0.0 | 0.671 |
| Adjusted factors Hypertension | ||||||||
| Yes | 5 | 1.03 (0.87-1.21) | 0.0 | 0.974 | 3 | 0.94 (0.71-1.23) | 0.0 | 0.746 |
| No | 7 | 0.84 (0.75-0.94) | 0.0 | 0.762 | 6 | 0.73 (0.54-0.97) | 36.7 | 0.162 |
| Smoking | ||||||||
| Yes | 9 | 0.91 (0.82-1.01) | 0.0 | 0.594 | 8 | 0.81 (0.64-1.02) | 33.9 | 0.158 |
| No | 3 | 0.82 (0.65-1.03) | 0.0 | 0.630 | 1 | 0.80 (0.48-1.31) | NA | NA |
| Obesity | ||||||||
| Yes | 10 | 0.89 (0.81-0.99) | 0.0 | 0.661 | 8 | 0.77 (0.65-0.91) | 9.9 | 0.353 |
| No | 2 | 0.89 (0.67-1.19) | 23.1 | 0.254 | 1 | 1.30 (0.72-2.36) | NA | NA |
Abbreviations: OC = oral contraception; RR = relative risk; CI = confidence interval; NA = not available.
a
Summary RRs (95% CIs) were calculated using the fixed or random effects model based on the results of I2-statistics.