Question

The incidence of disease X is 56/1,000 per year among smokers and 33/1,000 per year among nonsmokers. What proportion of cases of disease X are due to smoking among those who smoke? a. 56% b.33% C. 41% d. 23% e. 59%

Answer 1

C. 41 %

Explanation:

The proportion of cases of disease X that are due to smoking among those who smoke can be calculated using the formula for attributable risk (AR) among the exposed: AR = (incidence in exposed - incidence in unexposed) / incidence in exposed.

In this case, the incidence in exposed (smokers) is 56/1,000 and the incidence in unexposed (nonsmokers) is 33/1,000. Plugging these values into the formula, we get:

AR = (56/1000 - 33/1000) / (56/1000) = 23/56 ≈ 0.41

So the proportion of cases of disease X that are due to smoking among those who smoke is approximately 41%, which corresponds to answer choice C

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