There are substantial differences in respiratory symptoms and other respiratory illnesses, according to a study of patients with severe chronic obstructive pulmonary disease (COPD) on 3 continents.
COPD is one of the most common chronic respiratory diseases in the world, and previous research
found that COPD mortality increased 11.6% from 1990 to 2015 worldwide. During the same time period, the prevalence of COPD increased 44.2%.
“There are known ethnic differences in respiratory diseases including COPD,” the authors explained in their study published in International Journal of COPD
. “Geographic differences in severe COPD have not been widely studied, however.”
The study recruited 828 patients with severe COPD from Poland, The Republic of Korea (South Korea), and the United States. All participants completed a questionnaire and underwent standardized pre-bronchodilator and post-bronchodilator spirometry. Patients from Poland and South Korea were part of the Transcontinental COPD Genetics Study, and patients from the United States were part of the COPD Exacerbations Study. There were also 258 controls from Poland and South Korea who had normal spirometry.
Polish participants tended to be younger, while those from South Korea were almost entirely male, which the authors attributed to the fact that South Korean men have a historically higher rate of smoking than women. The Polish patients also had slightly more severe reductions in lung function.
In all 3 countries, respiratory symptoms and illnesses were assessed with the same questions, including:
- Do you usually have a cough?
- Do you usually bring up phlegm from your chest?
- Does your chest ever sound wheezy or whistling?
- Have you ever had an attack of wheezing that has made you feel short of breath?
Polish patients had higher rates of usual cough, usual phlegm, and chronic bronchitis, and South Koreans had more frequent attacks of wheezing. The researchers also found that South Koreans had high rates of a history of self-reported tuberculosis and physician-diagnosed asthma; Americans had a higher cumulative smoke exposure and an earlier age of smoking onset; and patients from Poland and the United States both had more frequent occupational exposures to gases or chemical fumes.
“Our results suggest that regional, racial, and environmental differences, as well as differences in diagnostic criteria and comorbidities, could be potential contributors to global COPD heterogeneity,” the authors concluded.