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Table 4 Limits on the gene-environment interaction factor (fge) and the proportion of the population in the high-genotypic risk group (γ).

From: A model of gene-gene and gene-environment interactions and its implications for targeting environmental interventions by genotype

Gene-environment interaction model Interaction factor fge Risk distribution Utility Uge Fraction of population at high genotypic risk
      Maximum γmax Minimum γmin
Genetic effect in high-exposure group only 1/PAFEe R 00 R ge Positive γmaxge (where PAFEge = PAFEe; PI = 1; and Uge = 1-γ). γminge (where Rge = 1).
   R 00 R 0e    
Multiplicative 1 R g0 R g0 R 0e /R 00   γmaxge = γ0 (where PAFEge = PAFEe; R00 = 0; and PAFGg = 1).  
   R 00 R 0e    
Additive 0 R g0 R g0 +R 0e -R 00 Zero γ0 (where R00 = 0).  
   R 00 R 0e    
Reverse multiplicative -rt/(1-rt) R g0 (1-R g0 ) (1- R 0e )/ (1-R 00 ) Negative   γneg = γminge (where PAFEge = 0 and Rge = 1)
   R 00 R 0e    
Genetic effect in low-exposure group only -ε/(1-ε)PAFEe R g0 R 0e    γneg (where PAFEge = 0 and PI = 0).
   R 00 R 0e