India has the highest number of people in the world with active tuberculosis. With the rising frequency of diabetes, where TB is endemic, there has been renewed interest in the question of whether diabetes increases the risk of active tuberculosis!
Well, diabetes not just triples the risk of developing active TB, but it is also a risk factor for adverse TB treatment outcomes. That's largely because diabetes is said to be immune-compromised which means that the patients tend to get more infections as they are low on immunity.
Therefore, the body's capability to fight microorganisms is impaired. Even hyperglycaemia, associated with pre-diabetes, can increase a person’s risk of developing an active TB.
Similarly, TB has an effect on diabetes too. It can not only worsen the control of blood sugar but also complicate the clinical management of diabetes. TB can, like most infectious diseases, worsen glycemic control through several pathogenic mechanisms related to the stress on the body caused by the infection, which can result in increased insulin resistance.
How diabetes affects TB severity
The chances of TB treatment failure, death and relapse after cure are high in patients who are also diabetic as immunity of such patients is really impaired battling two severe diseases. In fact, TB is typically associated with involvement of the upper lung field.
People with diabetes and TB are more likely to have lower lung field involvement and lung cavities. Lower lung field involvement can sometimes lead to misdiagnosis as pneumonia, carcinoma or abscesses. TB with lung cavities is associated with a higher risk of relapse, treatment failure and multi-drug resistance.
Furthermore, diabetes itself is associated with an increased risk of developing multi-drug resistant TB, which is rare to be treated.
Treatment of diabetes in TB patients
Optimal management of diabetes-associated TB begins with early case detection before the advanced progression of TB and the prevention of transmission through infection control. Therefore, treatment of patients with TB and diabetes usually follows the standard treatment regimen for drug-susceptible TB.
However, people with diabetes may respond differently to TB drugs, and may also have a higher body mass index than people without diabetes. Therefore, for the treatment of such patients, the drugs have to be optimised or modified as the medicines are usually given for TB can temporarily increase blood sugar levels.