Last update:
07-Jul-2004

Lung cancer is today the most frequent type of cancer worldwide. Smoking and asbestos are determinants of lung cancer frequency. Interaction between these two factors has been the subject of a great number of studies. The term “interaction” is encountered in statistics, epidemiology and pharmacology. In order to determine if there is statistical interaction between smoking and asbestos, researchers use statistical models, usually the additive model and, seldom, the multiplicative. In epidemiology the expression “effect measure modification” is used instead of the term “statistical interaction”. The presence or absence of effect measure modification depends on the arbitrary choice of effect measure. The effect measures usually used are the risk ratio (or the incidence density ratio) and the risk difference (or the incidence density difference). Apart from interaction with the meanings reported there also exists biological interaction, which refers to a mechanistic interaction which either exists or does not exist. Biological interaction can also be reported, more accurately, as biological coaction. More specifically, under the sufficient cause model, biologic co-action is defined as the participation of two or more component causes in the same sufficient cause that produces a disease via a specific mechanism. Biological co-action is defined as synergistic co-action or simply as synergism when the development of a disease requires the synergistic participation of two causal factors. Conversely, failure of a disease to occur because both factors are present is defined as antagonistic co-action between the two causal factors or antagonism. In order to determine if there is biological co-action between smoking and asbestos, researchers use a synergism index, S. If S is greater than one, then the two factors co-act for the disease occurrence. If S is less than one, then the two factors antagonize for the disease occurrence. If S equals one, then the two factors are biologically independent.

Key words: Asbestos, Biological interaction, Lung cancer, Smoking, Statistical interaction.