Convergence of the tuberculosis and diabetes epidemics: renewal of old acquaintances.

The current pandemic of type 2 diabetes mellitus (DM) is accelerating [1, 2] in a world where approximately one-third of the population is latently infected with Mycobacterium tuberculosis [3]. DM affects 230 million persons worldwide, and this number is anticipated to reach 366 million by 2030, at which time 80% of those affected will be living in low-and middle-income countries, where active tuberculosis (TB) is widespread [4, 5]. Eight of the 10 countries with the highest incidence of DM worldwide [5] are also classified as high-burden countries for TB by the World Heath Organization [6]. The consequences of these converging epidemics are likely to be substantial. The association between DM and TB was documented by Avicenna (who lived form 980 through 1027). During the early 20th century, it was said that a patient with diabetes who did not die in a diabetic coma was likely to die of TB, particularly if the patient was poor [7, 8]. The discovery of insulin in the 1920s and the later discovery of effective antibiotics led to the eclipse of the combination of these life-threatening diseases. Nevertheless, large surveys conducted prior to the 1960s indicated that TB was 2–4 times more prevalent in individuals with DM than in those without DM [7–10]. The patients' characteristics (e.g., onset of DM at young age and insulin use) suggested that at least one-half of the patients had type 1 DM [7, 9]. Today, with type 2 now accounting for 90%–95% of all cases of DM, we are " rediscovering " the association between TB and DM [11–21]. The current literature about TB and DM is sometimes contradictory and difficult to interpret. Most reports have limitations that are inherent in retrospective studies, lack confirmation of DM, or provide no measures of blood glucose control. Many contain data only on hospitalized patients, with bias towards the most seriously ill. Nevertheless, in the aggregate, the studies point to a significant impact of DM on TB, and these reports cannot be ignored. For example, data consistently reveal that the OR of patients with active TB who have type 2 DM ranges from 1.3-that DM clearly increases the risk of TB. Although, at the individual level, the risk of TB associated with DM is less than the risk of TB associated with AIDS (113-to 170-fold) [25, 26], the sheer number of patients with DM means that the associated risk of TB is …