As the incidence of tuberculosis and diabetes increases, a fresh look at the link between the two is needed.

Tuberculosis (TB) is an ancient disease and the earliest archaeological evidence of spinal TB was found in Egyptian mummies dating back to 2000.BC. The great Indian Physician Susruta was the earliest to note and comment on the association between diabetes and TB.

Before the discovery of insulin, a diagnosis of diabetes was like a death sentence within five years; and the most common cause of death was tuberculosis.

With the advent of insulin in early part of 20th century and with the availability of complete cure for TB, the association between the two was forgotten or perhaps grossly neglected.

But today, due to the diabetes pandemic, there is a “re-emergence” of the forgotten link. India has the largest number of people with diabetes in the world.

Rapid increase

The prevalence of Type2 diabetes has increased rapidly over the years especially in urban areas due to social and cultural changes, dietary changes, reduced physical activity, ageing population and other unhealthy behavioural patterns. Tuberculosis, on the other hand, is an infectious or communicable disease, and has been declared as the single largest killer by the WHO.

Sujatha, 34 years, was employed in a private firm and was supporting her family of four. She had been ill for some time and had rapid weight loss, fever and severe cough. She was diagnosed with tuberculosis and began anti-tuberculosis treatment through the DOTS programme. However she continued to feel tired with frequent urination and increased thirst. She was also not gaining weight, which made the physicians suspect concomitant underlying illness.

Investigations confirmed the diagnosis of diabetes. Sujatha was put on insulin to control her blood sugar levels and all her symptoms disappeared and she was able to attend to her routine work. There are many such people in the community who even succumb to the disease even before they are diagnosed with the deadly duo.

Patients with TB, who also have diabetes, may be more seriously ill and run the risk of relapse and treatment failure and may even pose a higher risk of spreading TB in the community.

Uncontrolled blood sugar levels have an adverse impact on TB treatment and leads to poor prognosis.

A systematic review of international research publications found that diabetes has strong association with TB. Studies among diabetes patients show a higher risk of developing TB due to impaired immunity. Sometimes there may be a reversal of the association, i.e. patients with TB may have increased insulin resistance and thereby run the risk of impaired glucose tolerance and diabetes is increased, in addition to the effect of some anti-TB drugs increasing blood sugar levels.

Dangerous impact

Whatever the pathway, the diabetes-tuberculosis duo will have a dangerous impact on public health.

The risk from HIV is well known, while HIV contributes to 3.4 per cent of adult TB incidence, in comparison, diabetes accounts for about 20.2 per cent of infectious TB incidence and 14.8 per cent of adult pulmonary TB incidence.

Today, there is more convincing epidemiologic evidence about the duo, and yet it is being largely ignored. None of the established guidelines/policies considers the relationship between the two diseases. It is high time that the double burden of diabetes and TB in developing country is recognised and given the utmost attention that it deserves.

The authors are Chennai-based diabetologists. E-mail: drvijay@mvdiabetes.com

Keywords: illnessTBdiabetesimmunity