European Journal of Epidemiology

, Volume 20, Issue 7, pp 575-579

First online:

Calculating measures of biological interaction

  • Tomas AnderssonAffiliated withStockholm Centre for Public Health Email author 
  • , Lars AlfredssonAffiliated withStockholm Centre for Public HealthInstitute of Environmental Medicine
  • , Henrik KällbergAffiliated withInstitute of Environmental Medicine
  • , Slobodan ZdravkovicAffiliated withInstitute of Environmental Medicine
  • , Anders AhlbomAffiliated withStockholm Centre for Public HealthInstitute of Environmental Medicine

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An editorial in this issue explains that the degree of biological interaction between risk factors is measured as the deviation from additivity by the corresponding disease rates and not for example as deviation from multiplicativity. It is the purpose of this article to describe how a logistic regression model, or a Cox regression model, can be defined in order to produce the output that is needed for assessment of biological interaction. We will also demonstrate how common software can be programmed to deliver this output. Finally, we show how this output can be used as input in an Excel sheet that is set up to calculate the measures of biological interaction to be used for the assessment.


Biological interaction RERI Synergy