Nutrition, diabetes and tuberculosis in the epidemiological transition

Abstract

Background: Diabetes prevalence and body mass index reflect the nutritional profile of populations but have opposing effects on tuberculosis risk. Interactions between diabetes and BMI could help or hinder TB control in growing, aging, urbanizing populations.

Methods and findings: We compiled data describing temporal changes in BMI, diabetes prevalence and population age structure in rural and urban areas for men and women in countries with high (India) and low (Rep. Korea) TB burdens. Using published data on the risks of TB associated with these factors, we calculated expected changes in TB incidence between 1998 and 2008. In India, TB incidence cases would have increased (28% from 1.7 m to 2.1 m) faster than population size (22%) because of adverse effects of aging, urbanization, changing BMI and rising diabetes prevalence, generating an increase in TB incidence per capita of 5.5% in 10 years. In India, general nutritional improvements were offset by a fall in BMI among the majority of men who live in rural areas. The growing prevalence of diabetes in India increased the annual number of TB cases in people with diabetes by 46% between 1998 and 2008. In Korea, by contrast, the number of TB cases increased more slowly (6.1% from 40,200 to 42,800) than population size (14%) because of positive effects of urbanization, increasing BMI and falling diabetes prevalence. Consequently, TB incidence per capita fell by 7.8% in 10 years. Rapid population aging was the most significant adverse effect in Korea.

Conclusions: Nutritional and demographic changes had stronger adverse effects on TB in high-incidence India than in lower-incidence Korea. The unfavourable effects in both countries can be overcome by early drug treatment but, if left unchecked, could lead to an accelerating rise in TB incidence. The prevention and management of risk factors for TB would reinforce TB control by chemotherapy.

Figure 1. Distribution of (A) population and (B) diabetes prevalence by BMI group, and (C) population and (D) new TB cases per 100,000 population in each age group in India in 1998 (filled bars) and 2005 (open bars).

Figure 2. Distribution of (A) BMI, (B) diabetes prevalence, and (C) population and (D) new TB cases per 100,000 population in each age group in Korea in 1998 (filled bars) and 2008 (open bars).

Figure 3. The net effects of nutritional and demographic changes on TB and TB among people with diabetes in (A) India and (B) Korea, expressed as the change over 10 years (1998–2008) in annual incidence (filled bars) and annual incidence per capita (open bars).

Errors bars are 95%CL.

Figure 4. Changes in the annual number of new TB cases between 1998 and 2008 in India (filled bars) and Korea (open bars) attributable to each of five factors (horizontal axis) acting separately.