Clinical implications of wheezing in patients with chronic obstructive pulmonary disease

Studies on the prevalence of wheezing in both the asthma-chronic obstructive pulmonary disease (COPD) overlap (ACO) and non-ACO groups, as well as the clinical characteristics of wheezing patients in each group, are rare. We examined the prevalence of wheezing in ACO patients and non-ACO patients, respectively. In addition, we aimed to determine clinical characteristics of patients with wheezing compared to those without wheezing in the ACO and non-ACO groups.

We analyzed the data from the Korean COPD Subgroup Study (KOCOSS), a multicenter prospective cohort. We classified patients into four groups according to whether they were ACO patients or had self-reported wheezing based on the patient's answer to the COPD-specific version of St. George's Respiratory Questionnaire (SGRQ-C): ACO with wheezing, ACO without wheezing, non-ACO with wheezing, and non-ACO without wheezing. Clinical characteristics and exacerbations during 1-year follow up were compared among four groups.

Wheezing was present in about 56% of patients in the ACO and non-ACO groups. In both groups, patients with wheezing exhibited more severe symptoms, worse lung function, and a higher risk of exacerbation than those without wheezing. There was no association between blood eosinophil count and wheezing in both the ACO and non-ACO groups. During 1-year follow-up, the ACO with wheezing group experienced exacerbations the most frequently, followed by the non-ACO with wheezing group. Moreover, wheezing was an independent predictor of the risk of exacerbation in patients with COPD, irrespective of both the ACO phenotype and the severity of airflow limitation. The exacerbation risk was higher in COPD patients who experienced wheezing more frequently.

Wheezing, reflecting more prominent airflow limitation and predicting exacerbation development, may serve as a severe phenotype of COPD rather than being indicative of an ACO phenotype.