Obese or overweight Chinese individuals 65 and older have a lower risk of developing tuberculosis than those at a normal weight, according to a study in the June 25 Archives of Internal Medicine.

Tuberculosis is commonly associated with poverty and undernutrition in both developed and developing countries. In addition, obesity is an increasing problem that is associated with a wide range of chronic degenerative conditions, notably, diabetes mellitus, a well-reported predisposing factor for active tuberculosis, according to the article.

The research team in the Tuberculosis and Chest Service in Hong Kong studied 42,116 individuals 65 or older enrolled in 18 health centers for elderly patients. Those with a BMI of less than 18.5 were grouped as underweight, 18.5 to less than 23 as normal, 23 to less than 25 as at risk for obesity, 25 to less than 30 as overweight, and 30 or higher as obese.

During the follow-up period, 477 cases of active tuberculosis were reported, 326 (68.3%) of which were confirmed using cultures of the bacteria involved. The average time between enrollment and notification of tuberculosis was 881 days.

There were 395 new cases (82.8%) and 82 retreatment cases (17.2%). Pulmonary involvement was found in 426 cases (89.3%) and extrapulmonary involvement in 87 (18.2%), including 36 cases (7.5%) with both.

Individuals who developed active tuberculosis were taller on average, but had a lower body weight and BMI (22.5 vs. 24.3) at the beginning of the study than those who did not. BMI outside the range of 18.5 to 23 decreased the active tuberculosis risk by 23.5 percent of the observed level. Baseline BMI obesity at 25 or above was associated with a 30.1 percent decrease in risk, whereas BMI lower than 18.5 increased the risk by 6.6 percent. A higher average initial BMI was found in pulmonary-only cases than in extrapulmonary-only cases (22.3 vs. 24.1).

Source: Emergency Medicine News:Volume 29(10)October 2007p 29