Using logistic regression in perinatal epidemiology: an introduction for clinical researchers. Part 2: the logistic regression equation

Summary. In Part 1 basic concepts were introduced as a preparation for an introductory explanation of logistic regression. Logistic regression is a statistical modelling technique, designed for the estimation of the simultaneous effects of predictors on the risk of a certain dichotomous outcome variable where each effect is estimated while adjusting for the effect of the other factors considered. The basic concepts - odds, odds ratio, confounding and interaction - were introduced in such a way that they naturally lead to the concept of logistic regression. In Part 2 the concepts are translated into simple equations. By studying these equations the equivalence between such mathematical expressions and the underlying clinical assessment of risk will become clear.