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Table 2 Estimates of incremental relative risks (IRRs) for bladder cancer of men obtained by three different methods

From: Age adjustment in ecological studies: using a study on arsenic ingestion and bladder cancer as an example

Predictors Direct Method Indirect Method Variable Method
  IRR [SE] IRR [SE] IRR [SE]
Arsenic Exposurea    
   0.05-0.08 mg/L -0.029 [0.021] -0.023 [0.017] -0.016 [0.010]
   0.09-0.16 mg/L 0.056 [0.030] 0.042 [0.024] 0.022 [0.013]
   0.17-0.32 mg/L -0.054 [0.039] -0.031 [0.032] -0.012 [0.017]
   0.33-0.64 mg/L 0.035 [0.045] 0.021 [0.036] 0.007 [0.020]
   > 0.64 mg/L 0.274 [0.036] 0.228 [0.029] 0.115 [0.016]
Urbanization Indexb 0.167 [0.046] 0.134 [0.037] 0.169 [0.040]
Cigarette Salec -0.047 [0.104] -0.026 [0.084] -0.006 [0.046]
Aged    
   20-29 years NAe NA 0.021 [0.019]
   30-39 years NA NA -0.050 [0.026]
   40-49 years NA NA -0.014 [0.035]
   50-59 years NA NA -0.041 [0.028]
   60-69 years NA NA 0.014 [0.028]
   > 69 years NA NA 0.037 [0.040]
p Value for the Modelf < 0.001 < 0.001 < 0.001
  1. aincremental relative risk for each 1% increase in residents exposed to arsenic levels in each exposure category.
  2. bincremental relative risk for each one-unit increase in urbanization index.
  3. cincremental relative risk for each 100 cigarettes sold per year.
  4. dincremental relative risk for each 1% increase in residents in each age group.
  5. enot included in the analyses.
  6. fp value for F test of the significance of the model.