Racial inequality in the annual risk of Tuberculosis infection in the United States, 1910-1933

Abstract

Tuberculosis (TB) mortality rates in the USA fell rapidly from 1910 to 1933. However, during this period, racial disparities in TB mortality in the nation's expanding cities grew. Because of long delays between infection and disease, TB mortality is a poor indicator of short-term changes in transmission. We estimated the annual risk of TB infection (ARTI) in 11 large US cities to understand whether rising inequality in mortality reflected rising inequality in ARTI using city-level TB mortality data compiled by the US Department of Commerce from 1910 to 1933. We estimated ARTI for African-Americans and whites using pediatric extrapulmonary TB mortality data for African-Americans and whites in our panel of cities. We also estimated age-adjusted pulmonary TB mortality rates for these cities. We find that the ratio of ARTI for African-Americans vs. whites increased from 2·1 (95% CI = 1·7, 2·4) in 1910 to 4·2 (95% CI = 3·4, 5·2) in 1933. This change mirrored the increasing inequality in age-adjusted pulmonary TB mortality during this period. These findings may reflect the combined effects of migration, inequality in access to care, increasing population density, and racial residential segregation in northern cities during this period.

Keywords: Historical epidemiology; Tuberculosis (TB); inequality; mathematical modelling; urbanization.

Fig. 1.

Age-standardized TB mortality rates for African-Americans and whites. The left-hand panel shows age- standardized TB mortality rates in the panel of cities from 1910 to 1933 in deaths per 100 K population. Black mortality rates are indicated by the solid line and white TB mortality rates by the dashed line. The right-hand panel shows the adjusted relative risk (ARR) of death from pulmonary TB for African-Americans vs. whites from 1910 to 1933. The vertical dashed line indicates the timing of the 1918 influenza pandemic. Shaded regions in both panels indicate 95% posterior credible intervals.

Fig. 2.

Annual risk of TB infection (ARTI) for African-Americans and whites, 1910–1933. The left-hand panel illustrates the ARTI for African-Americans (solid line) and whites (dashed line) from 1910 to 1933. The right-hand panel illustrates the ratio of the ARTI for African-Americans vs. whites during this period. The gray-shaded area in both panels illustrates the 95% posterior credible intervals (CIs) for these quantities.

Fig. 3.

New TB infections per prevalent pulmonary TB case, 1910–1933. The figure illustrates trends in the number of new TB infections among African-Americans (solid line) and whites (dashed line) for every prevalent pulmonary TB case during the period from 1910 to 1933. Areas shaded in gray indicate 95% posterior credible intervals.