Inter-relationship of different types of respiratory symptoms in COPD

Abstract

Aim

To examine the relationship between respiratory symptoms and their consistency across subgroups.

Methods

Data were analysed from two, 6-month aclidinium/formoterol combination studies. Respiratory symptoms were assessed by the Exacerbations of Chronic Pulmonary Disease Tool-Respiratory Symptoms (E-RS), the Early Morning Symptoms of COPD questionnaire and the Nighttime Symptoms of COPD questionnaire. The latter both evaluate individual symptoms (cough, wheezing, shortness of breath and difficulty bringing-up phlegm) and have an overall COPD symptoms item; also assessed were: limitation to activity (morning) and nocturnal awakening due to COPD (nighttime). Subgroups tested were sex, age, smoking status, severity of airway obstruction (postbronchodilator FEV₁/FVC <70 and FEV₁ ≥50% predicted or postbronchodilator FEV₁/FVC <70 and FEV₁ <50% predicted) and GOLD group. A principal-components factor analysis was used with factor rotation.

Results

The worst scores were: breathlessness, and early morning and nighttime cough and breathlessness. Two factors account for 83% of variance (F1: 72%; F2: 11%). F1 consisted of wheezing, breathlessness, overall COPD symptoms and limitation of activity; F2 contained cough and phlegm. Morning, daytime or night symptoms always loaded onto the same factor. Subgroups had the same pattern except GOLD A and C. In GOLD A, F1 (60% variance) was driven by cough and phlegm, and F2 (16% variance) by breathlessness. In GOLD C, F1 (57% variance) consisted of breathlessness, wheezing and awakenings; F2 (16% variance) contained cough and overall COPD symptoms.

Conclusions

Most COPD symptoms, regardless of time of day, group into a single factor; cough and phlegm form a second factor.