Summary of results
| Smoking status | No of studies | OR (95% CI) |
| A. Men | ||
| Ever smoker | ||
| Total | 7 | 1.89 (1.56 to 2.28) |
| Case–control studies | 6 | 1.87 (1.53 to 2.29) |
| Cohort studies | 1 | 2.04 (1.10 to 3.79) |
| Current smoker | ||
| Total | 7 | 1.87 (1.49 to 2.34) |
| Case–control studies | 6 | 1.89 (1.49 to 2.40) |
| Cohort studies | 1 | 1.60 (0.70 to 3.80) |
| Past smoker | ||
| Total | 5 | 1.76 (1.33 to 2.31) |
| Case–control studies | 4 | 1.79 (1.34 to 2.38) |
| Cohort studies | 1 | 1.40 (0.50 to 3.80) |
| B. Women | ||
| Ever smoker | ||
| Total | 12 | 1.27 (1.12 to 1.44) |
| Case–control studies | 7 | 1.27 (1.05 to 1.54) |
| Cohort studies | 5 | 1.27 (1.07 to 1.50) |
| Current smoker | ||
| Total | 12 | 1.31 (1.12 to 1.54) |
| Case–control studies | 6 | 1.19 (0.88 to 1.61) |
| Cohort studies | 5 | 1.37 (1.13 to 1.65) |
| Past smoker | ||
| Total | 10 | 1.22 (1.06 to 1.40) |
| Case–control studies | 5 | 1.24 (1.04 to 1.48) |
| Cohort studies | 5 | 1.20 (0.96 to 1.49) |
OR, odds ratio.