People with diabetes are at increased risk of developing tuberculosis (TB), according to a review of published studies. As a result, the increasing prevalence of diabetes may threaten global efforts to control TB, suggest researchers at Harvard School of Public Health in Boston in the latest issue of the journal PLoS (Public Library of Science) Medicine.

Experts have raised concerns about the merging epidemics of diabetes and TB, especially in low- to middle-income countries such as India and China, which are experiencing the fastest increase in diabetes cases and the highest burden of TB in the world, write Drs. Christie Y. Jeon and Megan B. Murray.

Searching for studies over the past four decades on the relationship between diabetes and TB, Jeon and Murray found 13 studies involving more than 1.7 million participants, including 17,698 cases of TB.

Combining the data from some of these studies, the researchers calculated that having diabetes increases the risk of active TB by about a factor of three. A three-fold increased risk suggests that diabetes may already be responsible for more than 10 percent of TB cases in India and China, Jeon and Murray note.

An association between diabetes and TB is biologically plausible, the researchers maintain, given research showing that diabetes impairs the immune system, making it harder for the body to fight off infection.

Based on the data, Jeon and Murray say, global TB control efforts "should consider targeting patients with diabetes." Increased efforts to diagnose and treat diabetes might decrease the global burden of TB, which kills about 1.6 million people each year, they suggest.

SOURCES: PLoS Medicine, July 2008, Reuters Health