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Table 3 Estimates of incremental relative risks (IRR) for women 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 -0.125 [0.045] -0.077 [0.030] -0.095 [0.046]
   0.09-0.16 mg/L 0.259 [0.062] 0.162 [0.041] 0.214 [0.063]
   0.17-0.32 mg/L -0.222 [0.082] -0.136 [0.055] -0.143 [0.082]
   0.33-0.64 mg/L 0.103 [0.094] 0.060 [0.062] 0.032 [0.093]
   > 0.64 mg/L 0.489 [0.075] 0.349 [0.050] 0.354 [0.076]
Urbanization Indexb 0.324 [0.097] 0.241 [0.064] 0.299 [0.212]
Cigarette Salec 0.011 [0.219] 0.009 [0.146] -0.004 [0.219]
Aged    
   20-29 years NAe NA 0.122 [0.153]
   30-39 years NA NA -0.249 [0.146]
   40-49 years NA NA 0.346 [0.217]
   50-59 years NA NA -0.170 [0.287]
   60-69 years NA NA 0.065 [0.373]
   > 69 years NA NA -0.417 [0.304]
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.