Characteristics of asthma and COPD overlap syndrome (ACOS) in the Canadian population.

OBJECTIVE: Asthma is a chronic disease affecting both children and adults, whereas chronic obstructive pulmonary disease (COPD) is a respiratory disease most commonly related to smoking and is usually seen in adults. When the airway disease shares features of both asthma and COPD, the phenotype is referred to as asthma and COPD overlap syndrome (ACOS). The objective of this cross-sectional study is to characterize ACOS in the Canadian population.

METHODS: Data from the first three cycles of the Canadian Health Measures Survey (CHMS) were used in this study. The study included 9059 subjects aged 30 years and above. The CHMS included a detailed interviewer-administered questionnaire and spirometry measurements. Based on the self-report, subjects were categorized into control, ACOS, COPD only and asthma only groups.

RESULTS: The prevalence of ACOS, COPD and asthma groups was 1.59%, 2.21% and 6.65%, respectively. The proportion of females was significantly greater than males in the ACOS group. The proportion of wheeze was highest in the ACOS group (64.93%) whereas the prevalence of shortness of breath was the highest in the COPD group (46.25%). Heart disease, cancer, arthritis and liver disease were more prevalent in the ACOS group than in COPD, asthma and control groups. Severity of airway obstruction was the highest in the ACOS group and was followed by COPD, asthma and control groups, respectively.

CONCLUSIONS: Characteristics of ACOS in the Canadian population were similar to those observed in the developed countries and longitudinal studies are required to determine the incidence and risk factors of ACOS.