The Potential Impact on Tuberculosis of Interventions to Reduce Undernutrition in the WHO South-East Asian Region: A Modelling Analysis

Abstract

Background: In order to meet the End TB targets in the WHO South-East (SE) Asia Region, it will be critical to achieve the prevention of TB at the population level. While progress towards the targets was already slow in the SE Asia Region, the COVID-19 pandemic reversed the gains. Undernutrition is a major risk factor accounting for almost 20% of TB incidence in the Region. In the absence of an effective vaccine, we sought to examine the potential impact of interventions to address undernutrition, on reducing TB burden in the Region.

Methods: We developed a deterministic, compartmental mathematical model, capturing undernutrition [Body Mass Index (BMI < 18.5kg/m2) and its associated excess risk of TB, calibrated to 10 out of 11 countries in the Region with the exception of the Maldives, which has low levels of undernutrition and of TB. For each country, the model also captured increases in TB burden arising from COVID-related disruptions. We simulated the potential impact, on TB incidence and mortality, of two types of interventions: (i) nutritional rehabilitation amongst all undernourished, close contacts of TB patients, and (ii) interventions to reduce the overall prevalence of undernutrition in the population, assuming a scenario where each country, 30% of people with undernutrition would be nutritionally rehabilitated each year. We simulated this impact both with and without additional measures to reduce diagnostic delays and improve treatment outcomes in the TB treatment cascade.

Results: The impact of nutritional interventions varies widely by country, depending on the existing prevalence of undernutrition. For example, in India nutritional interventions with 30% of undernourished population rehabilitated each year would avert 10.3% (95% CrI 8.1 – 13.3) of cumulative incidence between 2023 – 2030 when acting on their own, contrasting with 0.6% (95% CrI 0.0 – 4.5) for Bhutan, which has only 10.9% prevalence of undernutrition. Reductions in cumulative mortality range from 4.7% (95% CrI 3.2 – 8) for Bhutan, to 17.1% (95% CrI 13.9 – 19.9) for India. Comparable incremental reductions in TB burden arise when combined with measures to improve the TB cascade. Overall, nutritional interventions in the general population would increase incidence reductions by 2-3 fold, and mortality reductions by 5-6 fold, relative to targeting contacts.

Conclusion: Nutritional interventions could cause substantial reductions in TB burden in the Region, depending on the existing prevalence of undernutrition. The health benefits of such interventions extend well beyond TB, underlining their importance for public health.

Funding: SM worked in the capacity of an independent consultant. VB, SR are staff of the WHO South-East Asia Regional Office. AB is supported by Yenepoya Medical College. NA is supported by the UK Medical Research Council and the Bill & Melinda Gates Foundation. The authors did not receive any additional funding from another source for writing this manuscript.


Declaration of Interest: The authors declare no competing interest in production of this manuscript.

Keywords: Tuberculosis, Undernutrition, Preventions, WHO South-East Asian Region, Mathematical model