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September 23, 1974

Imprecise Incidents of Incidence

Author Affiliations

Rochester, Minn

JAMA. 1974;229(13):1724. doi:10.1001/jama.1974.03230510016013

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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