Iron–either too much or too little–linked with increased tuberculosis-related sickness or death

June 14, 2012 — Tuberculosis patients with iron levels that are either too low or too high may be at increased risk for faster disease progression or death, according to a Harvard School of Public Health (HSPH) study published May 11, 2012 in PLoS ONE.

Led by Sheila Isanaka, research fellow in the Department of Nutrition, researchers analyzed blood samples and data from 705 adults with tuberculosis—half HIV-infected, half not infected—in a randomized trial conducted in Dar es Salaam, Tanzania between 2000 and 2005. Participants were randomized to receive either a daily dose of micronutrients (not including iron) or a placebo.

They found that low levels of iron in blood were linked with an increased risk of treatment failure for all patients and of tuberculosis recurrence in HIV-infected patients. They also found that high levels of iron were associated with increased risk of death in all patients.

The new research suggests the potentially important role of iron in tuberculosis’ progression and severity, the authors said. They suggest that blood iron levels in tuberculosis patients could be more closely monitored. Routine screening of blood iron levels, they wrote, could be a useful tool for identifying tuberculosis patients at risk of poor outcomes and for targeting safe levels of iron supplements for treating anemia.

“This study confirms that iron imbalance exists in tuberculosis patients and is one of the first to show that both too little and too much iron may contribute to poor clinical outcomes,” said Isanaka. “Although the results of this study should be confirmed in larger cohorts with additional measures of iron status, these findings highlight the acute need to better understand the role of iron in the pathogenesis and progression of tuberculosis. Such advances could be of critical importance in improving the clinical management of more than nine million individuals newly infected with tuberculosis each year.”

Other HSPH authors of the study included senior author Wafaie Fawzi, professor of population sciences; professor of nutrition, epidemiology, and global health; and chair of the Department of Global Health and Population; Ronald Bosch; senior research scientist in the Department of Biostatistics; Walter Willett, professor and chair in the Department of Nutrition; Donna Spiegelman, professor of epidemiologic methods; and Christopher Duggan, associate professor in the Department of Nutrition.

–Karen Feldscher