A national study of socioeconomic status and tuberculosis rates by country of birth, United States, 1996-2005

Abstract

Background: Tuberculosis (TB) in developed countries has historically been associated with poverty and low socioeconomic status (SES). In the past quarter century, TB in the United States has changed from primarily a disease of native-born to primarily a disease of foreign-born persons, who accounted for more than 60% of newly-diagnosed TB cases in 2010. The purpose of this study was to assess the association of SES with rates of TB in U.S.-born and foreign-born persons in the United States, overall and for the five most common foreign countries of origin.

Methods: National TB surveillance data for 1996-2005 was linked with ZIP Code-level measures of SES (crowding, unemployment, education, and income) from U.S. Census 2000. ZIP Codes were grouped into quartiles from low SES to high SES and TB rates were calculated for foreign-born and U.S.-born populations in each quartile.

Results: TB rates were highest in the quartiles with low SES for both U.S.-born and foreign-born populations. However, while TB rates increased five-fold or more from the two highest to the two lowest SES quartiles among the U.S.-born, they increased only by a factor of 1.3 among the foreign-born.

Conclusions: Low SES is only weakly associated with TB among foreign-born persons in the United States. The traditional associations of TB with poverty are not sufficient to explain the epidemiology of TB among foreign-born persons in this country and perhaps in other developed countries. TB outreach and research efforts that focus only on low SES will miss an important segment of the foreign-born population.

Figure 1

TB rates by SES variables for foreign-born residents from the most common countries of origin. Each panel illustrates the association between TB rates and a different U.S. Census 2000 ZIP Code measure of SES for persons born in the Philippines, Vietnam, India, China, and Mexico. The U.S. Census defines education (Panel A) as the percentage of the population 25 and older in the Zip Code Tabulation Area (ZCTA) with any college attendance; crowding (Panel B) as the percentage of housing units in the ZCTA with more than one person per room; income (Panel C) as per capita income in the ZCTA in 1999; and unemployment (Panel D) as the percentage of the total population in the ZCTA area’s civilian labor force that was unemployed in 1999.