People with diabetes are at higher risk of developing tuberculosis (TB) than those without diabetes. Tuberculosis, an infectious disease of the lungs, affects 9.4 million people and kills 1.7 million worldwide every year. 1
TB is a major public health problem in many low- and middle-income countries, where the number of people with diabetes is also rising rapidly. Regions, such as Africa and Asia that are most heavily affected by tuberculosis are also those that have some of the highest numbers of people with diabetes (Map 4. 2 ), and will experience the biggest increases by 2030.
Growing double burden
The growing prevalence of diabetes poses a challenge for TB control as uncontrolled diabetes leads to a greater risk of developing TB. A recent study showed that countries that saw an increase in diabetes prevalence also had a significant increase in the number of people with TB. 2 This suggests that increasing diabetes prevalence could make attainment of the Millennium Development Goals on tuberculosis more difficult to achieve (Section 4.4).
These trends reflect the important links between the diseases. Several studies have looked at the association between diabetes and tuberculosis in developed countries 3 and found that people with diabetes are around 2.5 times more likely to develop tuberculosis. 4 These findings were also true of developing regions including Africa where one study found that the prevalence (%) of diabetes was twice as high in people with tuberculosis than in people without tuberculosis. 2
Map 4.2  shows estimates of the proportion of tuberculosis attributable to diabetes. In countries where the burden of diabetes is relatively high, for example Mexico, Egypt, Saudi Arabia and the United States of America, it is a significant contributor to the number of cases of tuberculosis. However, where rates of tuberculosis are high and diabetes is relatively low, diabetes contributes to a smaller proportion of the TB burden.
Treatment and screening
Not only does diabetes contribute to a person's risk of developing tuberculosis, but it also makes it more difficult to treat those who have both diseases. A review looking at the impact of diabetes on tuberculosis treatment found that people with diabetes are more likely to fail treatment and more likely to die during treatment compared to those without diabetes. 5
The link between tuberculosis and diabetes requires interventions that address both diseases. For example, screening for tuberculosis in people with diabetes and screening for diabetes in people with tuberculosis could offer opportunities to increase detection and prevent diabetes or tuberculosis-related complications.
A recent review showed that when people with diabetes were checked for tuberculosis, more people were found to have previously undiagnosed TB than in the general population. This was also true of people who had tuberculosis, and were checked for diabetes, in which many more were found to have previously undiagnosed diabetes than in the general population. 6
People with diabetes who have good glucose control are less likely to develop tuberculosis. 7 8 In addition, tuberculosis treatment leads to decreasing blood glucose levels 6 suggesting that integrated management of tuberculosis in people with high blood glucose could lead to better diabetes control.
Effective management of both diseases requires the same elements including early detection, providing guided standard treatment, and having an effective drug supply. The same principles can be applied to both diseases and help many people affected by tuberculosis and diabetes. Setting standards on these simple priorities could lead to effective detection and treatment for diabetes as has been seen in global tuberculosis control.
1: World Health Organization. Global tuberculosis control: 2010 Geneva: World Health Organization; 2010.
2: Goldhaber-Fiebert JD, Jeon CY, Cohen T, et al. Diabetes mellitus and tuberculosis in countries with high tuberculosis burdens: individual risks and social determinants. Int J Epidemiol 2011; 40 (2): 417-428.
3: Jeon CY, Murray MB. Diabetes mellitus increases the risk of active tuberculosis: a systematic review of 13 observational studies. PLoS Med 2008; 5 (7): e152.
4: Ottmani S.-E, Murray MB, Jeon CY, et al. Consultation meeting on tuberculosis and diabetes mellitus: meeting summary and recommendations. Int J Tuberc Lung Dis 2010; 14 (12): 1513-1517.
5: Baker MA, Harries AD, Jeon CY, et al. The impact of diabetes on tuberculosis treatment outcomes: A systematic review. BMC Med 2011; 9: 81.
6: Jeon CY, Harries AD, Baker MA, et al. Bi-directional screening for tuberculosis and diabetes: a systematic review. Trop Med Int Health 2010; 15 (11): 1300-1314.
7: Leung CC, Lam TH, Chan WM, et al. Diabetic control and risk of tuberculosis: a cohort study. Am J Epidemiol 2008; 167 (12): 1486-1494.
8: Pablos-Méndez A, Blustein J, Knirsch CA. The role of diabetes mellitus in the higher prevalence of tuberculosis among Hispanics. Am J Public Health 1997; 87 (4): 574-579.