Poisson Regression

Poisson regression models compare two exposure groups give identical rate ratios, confidence intervals and P-values to those derives using other methods. Poisson regression to control for confounding is closely related to other methods for rate ratios. We can estimate and control for the effects of vriables that change over time, by splitting the follow up time for each subject. Poisson regression models are fitted on a log scale. The results are then antilogged to give rate rations and confidence intervals. The principles and the approach are exactly the same as those for logistic regression(Kirkwood, p. 249).