Research conducted by the National Heart & Lung Institute, Imperial College, London, has identified a link between poverty and the increased mortality rates of those who suffer from COPD.

The study, which was published in Thorax, is based on analysis of data from 22 sites in the Burden of Obstructive Lung Disease (BOLD) study, which has already indicated that cigarette smoking prevalence is a good predictor for airflow obstruction.

However, using COPD mortality data from 170 countries, the new findings reveal a strong, inverse correlation between COPD and smoking when considering gross national income (GNI). According to the Imperial College study, when a country’s annual GNI fell below $15,000 per capita, rates of COPD mortality rose rapidly. What’s more, for 135 countries that fell under the low-income threshold, there was no clear association between the prevalence of smoking and COPD mortality.

Professor Peter Burney, head researcher for the Imperial College study, notes that the inverse association between airflow obstruction and smoking explains the lack of association between smoking and mortality from COPD. Instead, the findings suggest that forced vital capacity ratio may be low in poor countries due to ethnic differences, with the greatest relationship between income and the measurement in the most ethnically diverse populations.

“It is unlikely that the high mortality attributed to ‘COPD’, particularly in low-income countries, is associated with chronic airflow obstruction. It is much more likely to be associated with spirometric restriction,” Burney adds. “These analyses challenge us to rethink our notions and beliefs about the origins and significance of chronic lung disease and its prominent role as a major cause of death in low-income countries.”