The re-emerging association between tuberculosis and diabetes

Diabetes mellitus and tuberculosis are two major global health challenges whose intersection has been observed for more than a century. Historical records show that even before the discovery of insulin, TB was a frequent complication among patients with poorly controlled diabetes. Early studies, while limited in design, suggested that TB prevalence among diabetic patients was considerably higher than in the general population. This trend persisted across different eras and geographies.

The introduction of insulin therapy improved the survival of diabetic patients, inadvertently increasing the number of individuals who lived long enough to develop TB. Meanwhile, global shifts in lifestyle and nutrition led to a dramatic rise in obesity and type 2 diabetes, especially in regions where TB remains endemic. In contemporary times, some communities report that up to half of TB patients also have diabetes, underscoring the importance of this dual burden.

Beyond prevalence, disease severity and chronicity of diabetes have consistently emerged as key determinants of TB risk. Patients with prolonged hyperglycemia or a history of diabetic coma appear especially susceptible, likely due to compromised immune surveillance against Mycobacterium tuberculosis. This observation is consistent across older autopsy studies and modern epidemiological analyses.

Importantly, the association between TB and diabetes may not be unidirectional. While diabetes increases TB risk, evidence also suggests that TB can worsen glucose tolerance, either transiently through stress hyperglycemia or possibly by inflicting damage on pancreatic tissue. However, rigorous studies clarifying this pathway remain limited.

Treatment outcomes for patients with both diseases have historically been poor. Delays in diagnosis, limited therapeutic options, and socioeconomic disadvantage all contributed to high mortality rates among TB-DM patients in the past. Even today, diabetes remains a predictor of delayed TB clearance, treatment failure, and relapse.

Overall, the historical literature, despite its methodological limitations, provides valuable insights that remain relevant. It underscores the need for integrated strategies addressing both diabetes management and TB control, especially in low-resource settings where the co-occurrence of both conditions is increasingly common.

References:

1. Cadena, J., Rathinavelu, S., Lopez-Alvarenga, J.C. and Restrepo, B.I., 2019. The re-emerging association between tuberculosis and diabetes: lessons from past centuries. Tuberculosis, 116, pp.S89-S97.