No. of studies | Summary effect | Study heterogeneity | |||
---|---|---|---|---|---|
RR | 95% CI | P | I 2 | ||
Study design | |||||
Cohort | 5 | 1.25 | 0.95-1.65 | 0.002 | 75.7 |
Case–control | 7 | 2.15 | 1.41-3.26 | <0.001 | 89.1 |
Geographic location | |||||
Europe | 3 | 1.20 | 0.92-1.57 | 0.001 | 85.8 |
America | 5 | 1.73 | 1.15-2.60 | 0.014 | 67.8 |
Asia | 4 | 2.55 | 2.14-3.04 | 0.373 | 3.9 |
Gender | |||||
Male | 3 | 1.02 | 0.90-1.16 | 0.512 | 0.0 |
Female | 3 | 1.14 | 0.73-1.77 | 0.026 | 72.5 |