Interaction between continuous variables in logistic regression model

VernacularTitle:Logistic回归模型中连续变量交互作用的分析
Author: Hong QIU ¹ ; YU Tak-sun IGNATIUS ; TSE Ah LAP ; Xiao-Rong WANG ; Zhen-Ming FU
Author Information

1. 香港中文大学
Keywords: Logistic regression model; Continuous variableInteraction departure from additivity,Synergy index; Bootstrap
From: Chinese Journal of Epidemiology 2010;31(7):812-814
CountryChina
Language:Chinese
Abstract: Rothman argued that interaction estimated as departure from additivity better reflected the biological interaction. In a logistic regression model, the product term reflects the interaction as departure from multiplicativity. So far, literature on estimating interaction regarding an additive scale using logistic regression was only focusing on two dichotomous factors. The objective of the present report was to provide a method to examine the interaction as departure from additivity between two continuous variables or between one continuous variable and one categorical variable.We used data from a lung cancer case-control study among males in Hong Kong as an example to illustrate the bootstrap re-sampling method for calculating the corresponding confidence intervals.Free software R (Version 2.8.1) was used to estimate interaction on the additive scale.