Bangalore: A new study released on Tuesday shows that diabetes increases the risk of tuberculosis (TB) threefold, and the finding makes it important that India, which has the world’s highest population of people afflicted with both the conditions, carries out a systematic assessment of the association.
In Tuesday’s issue of PLoS Medicine, an open source academic journal, researchers from the Harvard School of Public Health, in their paper titled Diabetes Mellitus Increases the Risk of Active Tuberculosis, say diabetes could be contributing as much as 10% of TB cases in India and China.
“Our finding shows that tuberculosis occurs more often among people with diabetes than in those without. Thus, people with diabetes may be important targets to regularly screen for and treat active TB in areas of high TB incidence,” said researchers Christie Y. Jeon and Megan B. Murray in the paper.
According to a World Health Organization report released in March, India accounts for the largest share of 22% of the three million new TB cases in South-East Asia every year. Another report, by the World Economic Forum and Global Health Initiative, says India loses 100 million productive workdays every year due to TB, which according to the government’s own estimates, results in an economic cost of $3 billion (Rs12,840 crore) to the society.
Diabetes, on the other hand, is projected to affect 57 million Indians by 2025, according to a report by industry lobby group Assocham.
Clinicians say they have long observed the association between the two diseases, but haven’t effectively determined whether diabetes causes TB, or vice versa.
“We have known this for long, but due to limited resources, India has focused on fighting multi-drug resistant TB and other infectious diseases, and not cared to maintain a registry to track the correlation of the two diseases,” said V.M Katoch, director of the National Jalma Institute of Leprosy and Other Mycobacterial Diseases, an Agra-based institution that comes under the purview of the Indian Council of Medical Research, the government body that, according to its website, oversees “formulation, coordination and promotion of biomedical research” here.
This cannot be ignored for a long time, said Katoch. “The time has come to link the two biologically and epidemiologically as we have our catchment area where we can study this,” he added.
The new findings are also consistent with emerging scientific data on the biological mechanisms by which a diabetic condition called hyperglycemia (high blood sugar) may affect a person’s immune response (defence against an infection) to TB.
For their meta analysis, researchers studied research published over the last 40 years involving 1.7 million people across all geographic regions and found that the risk of TB increases regardless of the study design, geographic region, type of diabetes (I or II), and background TB incidence.
Researchers admit limitations to the study, which, among other things, has not studied how age and type of diabetes affects the causal relationship. So, they recommend further studies investigating how TB varies by type, duration and severity of diabetes. Experts, however, say the new finding is still an eye opener as India battles merging epidemics of diabetes and TB.