Chronic Obstructive Pulmonary Disease, or COPD, that results in emphysema or chronic bronchitis is the third leading cause of death worldwide but burden of disease is not shared equally between the sexes. Traditionally, men were more likely to be diagnosed but over the past two decades women have been catching up. In some cases, they make up to two thirds of diagnosed patients. Scientists and researchers pointed to the increase in urbanization and increasing smoking rates among women as a potential cause, but there might be another reason women struggle with lung disease: their airways are smaller. New research, published in the journal Radiology on August 2, found that women have disproportionately smaller airways than men, even when accounting for their smaller size overall.
“The prevalence of COPD in women is fast approaching that seen in men, and airway disease may underlie some of the high COPD numbers in women that we are seeing,” said the study’s lead author, Surya P. Bhatt, M.D., associate professor of medicine, Division of Pulmonary, Allergy and Critical Care Medicine at the University of Alabama at Birmingham and lead author on the study. “When airways narrow due to cigarette smoking, the impact on symptoms and survival is greater in women than in men.”
In this study, researchers analyzed data from nearly 10,000 participants enrolled in Genetic Epidemiology of COPD (COPDGene), a prospective multicenter observational cohort study of current, former and never smokers between 45 and 80 years old. The researchers studied CT scans to explore whether there was a sex-based difference in airway remodeling, or the narrowing of airways due to disease. They also wanted to see if there was any impact of airway remodeling on patient-reported outcomes including survival.
All participants underwent tests to assess lung function and answered questionnaires that determined the respiratory quality of life. To determine lung size, CT scans were analyzed airway wall thickness, total airway area and volume and also the diameter of the airway lumen. These results were adjusted for age, height, race, body mass index, pack-years of smoking, current smoking status and total lung capacity.
What they found was that women had smaller airways, even after accounting for height and total lung capacity in people who never smoked or those that smoked less than 100 cigarettes in their lifetime. In current and former smokers, men had greater airway wall thickness but larger airway lumens.
“The differences in airway dimensions even after adjusting for height and lung size, and the greater impact of changes in airway size on clinical outcomes in women, was remarkable in that women appear to have a lower reserve against developing airway disease and COPD,” said Bhatt.