Women with chronic obstructive pulmonary disease (COPD) have smaller airways leading to greater burden of respiratory morbidity and mortality, suggests a study published in the journal Radiology.¹

A secondary analysis of the prospective multicenter observational cohort Genetic Epidemiology of COPD study (COPDGene) was conducted to explore if structural differences in airways could explain the gender differences in the prevalence of COPD and the clinical outcomes. The study enrolled 9363 ever-smokers and 420 nonsmokers from January 2008 to June 2011, who were followed-up until November 2020. Their mean age was 60 years. Women comprised 57% and 46% of the nonsmoker and ever-smoker population. Those who had smoked less than 100 cigarettes in their life were categorised as non-smokers, while those who had smoked cigarettes within 30 days of the study entry were defined as ever-smokers. Seven parameters on CT scan were used to quantify the disease: airway wall thickness of segmental airways, Wall area percent of segmental airways, square root of the wall area of a hypothetical airway with 10-mm internal perimeter (Pi10), total airway count, Lumen diameter of segmental airways, airway fractal dimension and airway volume.

CT images showed that among the 420 never-smokers, the airway walls were thicker in men than in women as quantified for segmental airway wall area percentage (least-squares mean 47.68 vs 45.78). However, the dimensions of the airway lumen were lower in women compared to men as evidenced by segmental lumen diameter, which was 8.05 mm in women and 9.05 mm in men, after adjusting for height and total lung capacity.

Among the 9363 ever-smokers, the segmental airway wall area percentage was greater in men versus women; 52.19 vs 48.89, respectively. The segmental lumen diameter was again narrower in women than in men; 7.80 mm vs 8.69 mm.

The study also found that change in either of the measurements by one unit i.e. higher segmental airway wall area percentage or lower segmental lumen diameter reduced the forced expiratory volume in 1 second (FEV1)-to-forced vital capacity (FVC) ratio indicative of more severe airflow obstruction and the 6-minute walk distance; dyspnea was more severe with poor respiratory quality of life and survival in women compared to men. The total airway volume, total airway count and airway fractal dimension were lower in women. They also had narrower medium-size conducting airways.

COPD has generally been viewed as being more common in men. But recent data show a rising prevalence in women, who also have more severe symptoms such as dyspnea and are more likely to experience exacerbations than men. This study has shed some light on the possible explanation for this gender difference. According to this study, the airway lumen among nonsmoking women was smaller and further narrowing of the lumen as a result of cigarette smoking had a far worse impact on symptoms and survival in women compared to men. The study, however, stops short on inferring that the increase in respiratory morbidity and mortality in women were caused by smoking.

Reference

1. Surya P Bhatt, et al. Sex differences in airways at chest CT: results from the COPDGene cohort. Radiology. 2022 Aug 2;212985. doi: 10.1148/radiol.212985.