1918 influenza pandemic hastened the decline of tuberculosis in the United tates : An age , period , cohort analysis

The effect of the 1918 influenza pandemic on other diseases is a neglected topic in historical epidemiology. This paper takes up the hypothesis that the influenza pandemic affected the long-term decline of tuberculosis through selective mortality, such that many people with tuberculosis were killed in 1918, depressing subsequent tuberculosis mortality and transmission. Regularly collected vital statistics data on mortality of influenza and tuberculosis in the US are presented and analyzed demographically. The available population-level data fail to contradict the selection hypothesis. More work is needed to understand fully the role of multiple morbidities in the 1918 influenza pandemic. © 2011 Elsevier Ltd. All rights reserved. nfluenza uberculosis ge eriod ohort exis surface election . Background and introduction “During 1918 and 1919 there was a sharp upward trend to the curve [of tuberculosis death rates], followed in a year, or at most two years, by a marked downward direction of the curve—much steeper in its descent than that preceding 1917–1918. The pandemic of influenza of 1918–19 carried off, in a brief period, a large number of tuberculosis subjects that would otherwise have lived on and their deaths been so distributed through later years as not materially to have disturbed the uniform downward direction of the tuberculosis curve that precede the period of the great pandemic. ”—Abbot [1] We hypothesize that the 1918 influenza pandemic hastened the ecline of tuberculosis in the United States. The proposed mechaism is a harvesting effect whereby many people with tuberculosis ere killed during the increased mortality of 1918, thus reducng tuberculosis mortality and transmission in later years. This ∗ Correspondence address: Department of Sociology, 3151 Social Science Plaza, niversity of California, Irvine, 92697-5100 United States. Tel. : +1 949 824 7277. E-mail address: noymer@uci.edu 264-410X/$ – see front matter © 2011 Elsevier Ltd. All rights reserved. oi:10.1016/j.vaccine. 2011.02. 053 phenomenon was described by Abbot [1] (quoted above), and independently rediscovered by Noymer and Garenne [9]. This paper is an elaboration of that work. Routinely collected US vital statistics data on cause-specific mortality by age and sex for the first half of the twentieth century are presented. These data are analyzed to show that the most salient patterns of cause-, sex-, age-, and period-specific mortality are highly consistent with the proposed harvesting or selection mechanism. The available demographic data support the selection hypothesis in the US, but that more work is needed, especially along the lines of collecting representative individual-level data. The selective mortality hypothesis does not hold that tuberculosis alone was responsible for the severe mortality of the 1918 influenza pandemic. Annual winter influenza epidemics and high tuberculosis prevalence were present throughout the early twentieth century. Having both together did not create the unusual properties of the 1918 pandemic. The selective mortality hypothesis concerns the consequences of the pandemic for other diseases, especially tuberculosis, not the causes of the unusual severity of the 1918 pandemic. The selective mortality hypothesis views the 1918 influenza pandemic as a pivot point in the decline of tuberculosis in the US. Tuberculosis mortality was in decline in the US since at least the A. Noymer / Vaccine 29S (2011) B38– B41 B39 0 20 40 60 80 Age 50 100 200 400 80