Testing the influenza–tuberculosis selective mortality hypothesis with Union Army data

Abstract

Using Cox regression, this paper shows a weak association between having tuberculosis and dying from influenza among Union Army veterans in late nineteenth-century America. It has been suggested elsewhere [Noymer, A. and M. Garenne (2000). The 1918 influenza epidemic’s effects on sex differentials in mortality in the United States. Population and Development Review 26(3), 565–581.] that the 1918 influenza pandemic accelerated the decline of tuberculosis, by killing many people with tuberculosis. The question remains whether individuals with tuberculosis were at greater risk of influenza death, or if the 1918/post-1918 phenomenon arose from the sheer number of deaths in the influenza pandemic. The present findings, from microdata, cautiously point toward an explanation of Noymer and Garenne’s selection effect in terms of age-overlap of the 1918 pandemic mortality and tuberculosis morbidity, a phenomenon I term “passive selection”. Another way to think of this is selection at the cohort, as opposed to individual, level.

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“…Researchers have suggested ways to model frailty distributions, which might allow us to make better sense of observed aggregate mortality hazards (e.g., Aalen 1994;Steinsaltz and Wachter 2006;Vaupel and Carey 1993;Vaupel and Yashin 1985;Zahl 1997). Noymer (2009) suggests examining the interaction of different diseases as one way of studying the association between observed death rates and frailty distributions, as exposure to one disease can enhance mortality risk to another.…”

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