An epidemiological investigation into an epidemic of lung cancer among uranium miners in the Czech Republic demonstrated a synergistic (supramultiplicative) interaction between radon gas exposure and cigarette smoking. In a 2×2 interaction table, which model of interaction does this BEST illustrate?
- A Additive interaction model (public health relevant synergy)
- B Antagonism under the additive model
- C Multiplicative interaction model with positive departure from multiplicativity ✓
- D Negative confounding between radon and smoking
Explanation
Radon-smoking synergy for lung cancer is one of the best documented examples of positive interaction (synergism) exceeding the multiplicative model — i.e., the combined risk is greater than the product of individual risks (supramultiplicative, also called positive departure from multiplicativity). Under the additive model, synergy means the combined effect exceeds the sum of individual effects. The radon-smoking interaction exceeds even the multiplicative expectation, demonstrating biological synergy at the level of DNA damage repair. This distinction is important: public health relevance often uses the additive model (RERI, AP, S indices), while epidemiological multiplicative excess risk ratio captures supramultiplicativity.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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