Table 2

χ2 Woolf and p value for homogeneity, pooled estimates of prostate cancer risk, and 95% CIs for several groupings of the data

PooledHomogeneity
GroupingNo. studiesNo. risk estimatesRate ratio95% CIχ2 Woolfp value
No. risk estimates = number of estimators of relative risk, (fixed) = fixed effects estimates, otherwise random effects estimates. PMR, proportional mortality ratio; SMR, standardised mortality ratio; SIR, standardised incidence ratio; OR, odds ratio; MOR, mortality odds ratio; HWE, healthy worker effect (significantly lower than expected all-cancer mortality or incidence). *In the study of Aronson et al (1996), the control group consisted of the pool of cancer controls and population controls; pooled rate ratios are in bold when the 95% CI does not include 1. †In this subset analysis, only studies reporting RR estimators for prostate cancer as well as for all cancer were included.
All studies
All studies (cohort, case-control, PMR)2225 1.13 1.04 to 1.22370.727<0.001
All studies excluding PMR1821 1.09 1.00 to 1.19271.805<0.001
Study design
Cohort
All studies1114 1.13 1.02 to 1.24236.773<0.001
    SMR441.370.81 to 2.3215.1560.002
    SIR7101.060.97 to 1.17189.255<0.001
Case-control
All studies770.980.71 to 1.3734.948<0.001
    OR661.060.76 to 1.4818.2940.003
    MOR11 0.7 0.6 to 0.9
Geographic location
Europe
All studies9120.980.93 to 1.0238.595<0.001
    Cohort690.980.94 to 1.0334.229<0.001
        SMR220.930.60 to 1.420.1040.747 (fixed)
        SIR470.980.94 to 1.0334.061<0.001
    Case-control
        OR33 0.73 0.55 to 0.970.4060.816 (fixed)
US/Canada
All studies88 1.50 1.08 to 2.0788.134<0.001
    Cohort44 1.93 1.76 to 2.134.8600.182 (fixed)
        SMR22 1.89 1.13 to 3.164.0520.044
        SIR22 1.90 1.71 to 2.110.2020.653 (fixed)
    Case-control441.210.75 to 1.9629.578<0.001
        OR33 1.43 1.20 to 1.712.5840.275 (fixed)
        MOR11 0.7 0.6 to 0.9
Others
    SIR11 0.61 0.37 to 0.95
Outcome
Incidence
All studies13161.070.98 to 1.17212.611<0.001
    SIR7101.060.97 to 1.17189.255<0.001
    OR661.060.76 to 1.4818.2940.002
Mortality
All studies551.150.63 to 2.1156.339<0.001
    SMR441.370.81 to 2.3215.1560.002
    MOR11 0.7 0.6 to 0.9
Reference population
Cohort studies
National/regional1114 1.13 1.02 to 1.24236.773<0.001
PMR44 1.23 1.09 to 1.3826.945<0.001
Case to control
Hospital220.760.56 to 1.040.0270.870 (fixed)
Cancer11 1.43 1.161 to 1.761
General population330.950.47 to 1.9512.5070.0019
Cancer + general population*111.180.77 to 1.81
Healthy worker effect (HWE)†
Cohort studies (SMR+SIR) + HWE69 1.15 1.01 to 1.31218.445<0.001
Cohort studies (SMR+SIR) − HWE220.860.58 to 1.280.5470.460 (fixed)
Occupation category
Pesticide applicators44 1.64 1.13 to 2.3864.697<0.001
Farmers11140.970.92 to 1.0362.381<0.001
    USA/Canada551.260.83 to 1.9031.355<0.001
    Europe690.960.92 to 1.0128.923<0.001
Prostate cancer versus all cancer
All cancer811 0.80 0.77 to 0.84128.275<0.001
Prostate cancer8111.120.99 to 1.27219.413<0.001