Pooled | Homogeneity | |||||
---|---|---|---|---|---|---|
Grouping | No. studies | No. risk estimates | Rate ratio | 95% CI | χ2 Woolf | p value |
No. risk estimates = number of estimators of relative risk. RR, relative risk; PMR, proportional mortality ratio. *The study of Andersen et al (1999), Norway21 was substituted by the study of Kristensen et al (1996)34; the study of Andersen et al (1999), Finland21 was substituted by the study of Pukkala and Notka (1997)40; the study of Andersen et al (1999), Sweden21 was substituted by the study of Wiklund and Dich (1995).48 †Studies included were Settimi et al (1998),43 Thomas et al (1996),46 and Zahm (1997).49 Pooled rate ratios are in bold when the 95% CI does not include 1. | ||||||
All studies | ||||||
All studies excluding PMR | 18 | 21 | 1.09 | 1.00 to 1.19 | 271.805 | <0.001 |
Deleting studies with extreme RR values | ||||||
Largest value | ||||||
Fleming et al (1999) [30] | 17 | 20 | 1.05 | 0.96 to 1.14 | 226.675 | <0.001 |
Smallest value | ||||||
Andersson et al (1996) [55] | 17 | 20 | 1.10 | 1.01 to 1.20 | 269.724 | <0.001 |
Deleting studies with extreme precision values | ||||||
Largest value | ||||||
Andersen et al (1999) Sweden [21] | 18 | 20 | 1.10 | 1.00 to 1.22 | 258.064 | <0.001 |
Smallest value | ||||||
Sperati et al (1999) [45] | 17 | 20 | 1.09 | 1.00 to 1.20 | 271.609 | <0.001 |
Substitution by redundant studies* | 21 | 21 | 1.08 | 0.98 to 1.20 | 283.062 | <0.001 |
Inclusion of studies reporting less than 5 exposed cases† | 21 | 24 | 1.09 | 1.00 to 1.19 | 274.300 | <0.001 |