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The article by Zisman et al¹ seems to rely on the assumption that age at diagnosis reflects important influences on disease occurrence. This is not true in general. For example, if smokers are younger than nonsmokers, then the age at diagnosis of many diseases will tend to be younger in smokers than in nonsmokers simply because of the age difference between these 2 groups of individuals.

The age-at-diagnosis fallacy has been a subject of interesting comment previously. Rothman² provided a clear illustration of the difficulties this line of reasoning can lead to. Would one conclude that nursery school is more dangerous than paratrooper training because the mean age at death among the nursery school attendees is lower than that of the army trainees? Certainly not. What matters, of course, are the disease rates in the 2 groups.

AUTHOR INFORMATION
Correspondence: Dr Baron, Dartmouth Medical School, Evergreen Center, 46 Centerra Pkwy, Suite 300, . . . [Full Text of this Article]

John A. Baron, MD

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