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To the Editor.—
Dr. Lester's letter entitled "The Suicide Capital of America" (228:1637, 1974) represents another example of the many imprecise incidents of incidence in the medical literature. To the epidemiologist, the term incidence has a very specific meaning, namely, the number of new cases of a particular disease reported over a given period of time divided by the population at risk for the disease over the same period of time. Since a successful suicide attempt always results in death, the incidence rate also represents a mortality rate. The incidence of suicide should not be expressed (as suggested by Lester) as a percentage of all deaths in a given year and locale. This latter measure is more properly termed a "cause-specific death ratio," "cause of death ratio," or "proportional mortality ratio." The fact that the incidence of suicide and the proportional mortality ratio for suicide are related when analyzed by
Schoenberg BS. Imprecise Incidents of Incidence. JAMA. 1974;229(13):1724. doi:10.1001/jama.1974.03230510016013