Series
The effect of diabetes and undernutrition trends on reaching 2035 global tuberculosis targets

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Summary

To achieve the post-2015 global tuberculosis target of 90% reduction in tuberculosis incidence by 2035, the present rate of decline must accelerate. Among factors that hinder tuberculosis control, malnutrition and diabetes are key challenges. We review available data to describe the complex relationship between tuberculosis, diabetes, and nutritional status. Additionally, we review past trends, present burden, and available future global projections for diabetes, overweight and obesity, as well as undernutrition and food insecurity. Using a mathematical model, we estimate the potential effect of these factors on tuberculosis burden up to 2035. Great potential exists for reduction of worldwide tuberculosis burden by combination of improved prevention and care of diabetes with reduction of undernutrition. To achieve this combination will require joint efforts and strong cross-programme links, enabling synergistic effects of public health policies that promote good nutrition and optimum clinical care for tuberculosis and diabetes.

Introduction

In May 2014, the 67th World Health Assembly passed a resolution on the global strategy and targets for tuberculosis prevention, care, and control after 2015.1 During the past two decades, global efforts to control tuberculosis have resulted in cure of 56 million patients and reduced tuberculosis mortality substantially.2 However, tuberculosis remains a major global public health concern, accounting for 8·6 million new cases, 1·3 million deaths,2 and more than 49 million disability-adjusted life-years (DALYs) lost every year.3 Additionally, the tuberculosis epidemic has vast social effects, with a particularly high burden on the poor,2 which is not captured by mortality, incidence, and DALY indicators.

The three pillars of the new global tuberculosis strategy are: integrated, patient-centred care and prevention; bold policies and supportive systems; and intensified research and innovation. The strategy has a renewed focus on prevention, and its components include, among others, management of comorbidities, action on tuberculosis risk factors and underlying determinants, and treatment of latent tuberculosis infection (LTBI) for people at high risk.4 Undernutrition and diabetes are identified as among the main challenges for effective tuberculosis care and prevention.4 Both factors increase the risk of development of active tuberculosis by about three times; they also increase risk of poor tuberculosis treatment outcomes, including death, treatment failure, and relapse.5, 6, 7, 8, 9 At the same time, these factors are linked elements of individuals’ nutritional profiles. Changes in the prevalence and distribution of diabetes and undernutrition at the global level—in the context of the ongoing epidemiological transition—are likely to affect future tuberculosis burden.10, 11

The post-2015 global tuberculosis targets include reduction of tuberculosis incidence by 90% by 2035.4 To achieve this target, an acceleration of the present rate of tuberculosis decline is needed.12, 13 Thus, it is crucial to understand how changing trends in important tuberculosis determinants such as diabetes and undernutrition will affect progress towards the new targets. Additionally, it is important to determine what actions are needed to move towards integration of tuberculosis control with improved nutrition and prevention and management of non-communicable diseases (NCDs);14 such actions will likely include strengthening of health systems at many levels and social protection.13

Actions to address diabetes and undernutrition are already incorporated into the post-2015 global tuberculosis strategy.1, 13 However, the potential effect of those actions on global tuberculosis epidemiology has not previously been assessed. In this Series paper, we first review epidemiological and biological evidence to describe the complex relationship between tuberculosis, diabetes, and nutritional status. We then review at the global level: past trends; present burden and future projections in diabetes, overweight, and obesity; and undernutrition and food insecurity. Last, we estimate how different scenarios (table; panel 1) of future trends for diabetes and undernutrition could affect tuberculosis epidemiology until 2035, and discuss implications for synergistic actions to address these determinants.

Section snippets

Nutritional status, diabetes, and tuberculosis

Solid epidemiological evidence indicates that poor nutritional status is a risk factor for tuberculosis,8, 9 and the biological basis of the relationship has been well described.8 Data from studies in humans and animals show that vulnerability to progression from tuberculosis infection to active tuberculosis is related to macronutrient deficiencies that induce impairment of cellular immunity, and that this impairment is rapidly reversed with nutritional rehabilitation.8 Improved nutritional

Global burden and past trends in the context of the ongoing epidemiological transition

12% of the global population is undernourished,47 37% of adults are overweight or obese,48 and 8·3% of adults have diabetes.49 The prevalence of global undernourishment decreased from 18·9% in 1990–92 to 12·0% in 2011–13, approaching the third target of the UN Millennium Development Goal 1, which was to halve the proportion of people who suffer from undernourishment between 1990 and 2015.50 Although globally the number of undernourished people has reduced overall, different rates of progress

The effect of diabetes

We created an analytical model to estimate the effect of diabetes and undernutrition on projected tuberculosis epidemiology until 2035 under different scenarios (Panel 1, Panel 2). In 2011–12, tuberculosis incidence decreased globally by 2%;2 if this small decrease persists in a linear way, by 2035 tuberculosis incidence will be decreased by about 40% compared with 2012. This would correspond with an annual disease incidence of about 72 per 100 000 people in 2035, which is far below the agreed

Conclusion

Reduction of undernutrition and better prevention and care for diabetes could produce a large preventive effect on tuberculosis. Our analysis suggests that eradication of undernutrition would be especially effective in the African and southeast Asian regions, and lead to further decreases in 2035 tuberculosis incidence by 31% and 23%, respectively, compared with the present trajectory of decline. Better prevention and care for people with diabetes has the strongest potential to affect

Search strategy and selection criteria

We searched Medline and Embase up to May 29, 2014, using combinations of free text and Mesh terms for “diabetes mellitus”, “nutritional status”, “malnutrition”, “overweight”, “obesity”, and “tuberculosis” in a comprehensive search strategy, without language restrictions. We applied no limits to the search strategy. Original studies of any design, narrative and systematic review, meta-analyses, expert consultation reports, consensus papers, and book chapters were considered. We prioritised the

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