An association has been identified between newly diagnosed active tuberculosis (TB), diabetes, and body mass index (BMI), according to a study published in BMC Infectious Diseases. For overweight or obese adults, diabetes was the highest risk factor for active TB.

Between 2014 and 2018, investigators conducted a cross-sectional study on 2032 patients in southern India, 919 of whom had newly diagnosed active TB and 1113 of whom were household contacts of an individual with TB. Demographic and health data were collected upon each participant’s enrollment, as were physical features, BMI, and TB testing. Additive and multiplicative BMI-diabetes interactions with active and latent TB were evaluated using generalized estimating equations, with adjustments for age and sex. Household contacts without diabetes, a normal BMI and no latent TB infection were used as the reference group. 

Researchers highlighted that incident TB infection is associated with transient hyperglycemia, which can resolved with TB treatment without therapy for glycemic control. In fact, overall 49% of patients with TB had a random blood glucose >140 mg/dL. Further, of the 344 participants with diabetes who received random blood glucose testing, 72% had a measurement ≥200 mg/dL and 6% of those who had not been diagnosed with diabetes had random blood glucose ≥200 mg/dL. Of participants who did not have a previous diagnosis of diabetes, and demonstrated random blood glucose ≥200 mg/dL 32% were overweight or obese.

Compared with patients who did not have diabetes, researchers found that patients with diabetes had a 2.13-times higher adjusted prevalence of active TB. Researchers also noted weight stratification among patients with diabetes: those who were overweight or obese had a 12-times higher prevalence (P <.0001), whereas patients who were underweight had a 1.04-times higher prevalence. In patients who were overweight or obese and did not have diabetes, the adjusted risk for active TB was 0.17-times that of patients with normal BMIs. In addition, diabetes was linked to latent TB infection in participants who were underweight.

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Limitations to this study included a cross-sectional design, the exclusive recruitment of participants with type 2 diabetes who were aged >18 years, little reliability in low-BMI estimates, a reduction in tubercular skin test specificity resulting from bacille Calmette-Guérin vaccination, and the use of household contacts instead of community members for controls.

Through the findings, study researchers “highlight the high prevalence of diabetes among active [tuberculosis] patients at all levels of BMI in this south Indian cohort. Malnutrition as measured by BMI was also associated with a higher burden of [tuberculosis], primarily among those without diabetes. BMI and diabetes were not major risk factors for [latent TB infection].”

Reference

Kubiak RW, Sarkar S, Horsburgh CR, et al. Interaction of nutritional status and diabetes on active and latent tuberculosis: a cross-sectional analysis. BMC Infect Dis. 2019;19:627.