According to recent studies and experts, Diabetes Mellitus (DM) increases the risk of TB disease by two to three times. This association may be even stronger when other risk factors, such as HIV infection or smoking, are present. The increased risk of tuberculosis is evident in both type 1 DM and type 2 DM.
Dr. Rahul Kendre, Consultant Lung Transplant Surgeon at DPU Private Super Specialty Hospital, explained in a conversation with WION that DM is a significant risk factor for Multi-Drug Resistant TB. He mentioned that diabetes contributes to increased susceptibility to tuberculosis through various mechanisms, including hyperglycemia and cellular insulinopenia. These factors have indirect effects on macrophage and lymphocyte function, suppressing cell-mediated immunity and allowing latent tuberculosis to become active.
Dr. Rahul clarified that while TB does not cause DM, it may reveal individuals at risk of developing DM in the future. TB is associated with glucose intolerance and hyperglycemia, both of which automatically resolve with TB treatment. Studies have shown that up to 50 percent of TB patients with high blood glucose levels at diagnosis return to normal levels after TB treatment. TB also impairs glycemic control in patients with previously known DM, requiring higher insulin doses and oral hypoglycemic medications.
Approximately 15 percent of tuberculosis cases worldwide may be linked to DM. The reported prevalence of tuberculosis among DM patients ranges from 0.38 percent to 14 percent, with an overall median prevalence of 4.1 percent.
One study found that the risk of active tuberculosis was three times higher in DM patients with a hemoglobin A1c (HbA1c) level greater than or equal to 7 percent compared to those with an HbA1c level below 7 percent.
Insulin dependence is also considered a risk factor for tuberculosis. The Philadelphia Diabetic Survey revealed that the likelihood of developing tuberculosis was twice as high among DM patients using more than 40 units of insulin per day compared to those using lower doses.
Symptoms of TB disease depend on where the TB bacteria are growing in the body. Typically, TB bacteria grow in the lungs (pulmonary TB) and may cause symptoms such as a persistent cough lasting three weeks or longer, chest pain, and coughing up blood with sputum.
Other symptoms of TB include weakness or fatigue, loss of appetite, weight loss, low-grade evening fever, and night sweats.
Dr. Rahul concluded that active TB disease may present atypically in individuals with DM, and TB may progress faster in such cases. The effects of DM on chest radiograph findings are inconsistent, with some studies describing more frequent isolated lower lung field lesions and an increase in consolidation and cavities in Pulmonary TB patients with DM, sometimes resembling the radiographic pattern seen in HIV.
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