Abstract

Background There is good evidence that diabetes is a risk factor for pulmonary tuberculosis. In England, the rates of both diabetes and tuberculosis vary markedly by ethnic group.

Objective To estimate the proportion of incident cases of pulmonary tuberculosis attributable to diabetes (population attributable fraction, PAF) for Asian, black and white men and women aged ≥15 years in England.

Methods An epidemiological model was constructed using data on the incidence of tuberculosis, the prevalence of diabetes, the population structure for 2005 and the age-specific relative risk of tuberculosis associated with diabetes from a large cohort study.

Results The estimated PAF of diabetes for pulmonary tuberculosis is highest for Asian men (19.6%, 95% CI 10.9% to 33.1%) and women (14.2%, 95% CI 7.1% to 26.5%). The PAF for all ages is similar in white and black men (6.9%, 95% CI 3.1% to 12.4% and 7.4%, 95% CI 4.6% to 12.9%, respectively) and women (8.2%, 95% CI 3.0% to 15.6% and 8.9%, 95% CI 5.3% to 15.6%, respectively). The similarity of these overall figures, despite a higher prevalence of diabetes in the black population, reflects a much younger mean age of pulmonary tuberculosis in the black population. Overall, of 3461 new cases of pulmonary tuberculosis in England in 2005, 384 (202–780) were estimated to be attributable to diabetes.

Conclusion Given the nature of the data available, considerable uncertainty surrounds these estimates. Nonetheless, they highlight the potential importance of diabetes as a risk factor for pulmonary tuberculosis, particularly in groups at high risk of both diseases. Further research to examine the implications of these findings for tuberculosis control is urgently needed.