Subgroups | No. of studies | OR (95% CI) | I2 | P |
---|---|---|---|---|
Overall | 7 | 0.83 (0.7–0.98) | 45.9 | 0.089 |
Target population | Â | Â | Â | Â |
 Female | 2 | 0.75 (0.53–1.07) | 61.1 | 0.109 |
 Male + female | 5 | 0.88 (0.69–1.13) | 53.0 | 0.075 |
Area | Â | Â | Â | Â |
 USA | 3 | 0.77 (0.68–0.87) | 1.5 | 0.362 |
 Europe and Canada | 2 | 0.88 (0.73–1.07) | 0 | 0.686 |
 Asia | 2 | 1.21 (0.50–2.90) | 80.7 | 0.023 |
Development level | Â | Â | Â | Â |
 Developed country | 6 | 0.80 (0.73–0.88) | 0 | 0.614 |
 Developing country | 1 | 1.94 (1.04–3.62) | - | - |
Study design | Â | Â | Â | Â |
 Cohort | 1 | 0.87 (0.71–1.07) | - | - |
 Case control | 6 | 0.83 (0.66–1.04) | 53.0 | 0.059 |
  Hospital-based | 4 | 0.86 (0.62–1.19) | 68.9 | 0.022 |
  Population-based | 2 | 0.79 (0.57–1.08) | 0 | 0.324 |
Smoking assessment | Â | Â | Â | Â |
 Interview | 5 | 0.88 (0.69–1.13) | 53.0 | 0.075 |
 Questionnaires | 2 | 0.75 (0.53–1.07) | 61.1 | 0.109 |
OR type | Â | Â | Â | Â |
 Crude | 2 | 0.75 (0.53–1.07) | 61.1 | 0.109 |
 Adjusted | 5 | 0.88 (0.69–1.13) | 53.0 | 0.075 |