Longitudinal comparison of outcomes in patients with smoking-related asthma-COPD overlap and in non-smoking asthmatics with incomplete reversibility of airway obstruction

BACKGROUND: There is a need to characterize the impact of the smoking status on the clinical course of asthmatics with incomplete reversibility of airway obstruction (IRAO). OBJECTIVE: To compare longitudinal health care use, symptom control, and medication needs between smoking and non-smoking asthmatics with IRAO. MATERIALS AND METHODS: This was a 12-month follow-up of a cross-sectional study comparing asthmatics with IRAO according to their tobacco exposure. One group had a tobacco exposure ≥20 pack-years and was considered to have asthma-COPD overlap (ACO) and the second with a past tobacco exposure <5 pack-years was considered as non-smokers with IRAO (NS-IRAO). Study participants were contacted by telephone every 3 months to document exacerbation events and symptom control. RESULTS: A total of 111 patients completed all follow-up telephone calls: 71 ACO and 40 NS-IRAO. The number of exacerbations per patient over the 12-month follow-up was similar in both groups. However, ACO reported worse symptom control throughout the follow-up as compared to NS-IRAO, although no significant variations within a group were observed over the study period. CONCLUSION: Although asthma control scores were poorer in ACO patients over 1 year compared to NS-IRAO, exacerbation rate was similar and low in both groups of asthmatics. These observations suggest that poorer asthma control in ACO was not driven by the number of exacerbations but may reflect the influence of chronic airway changes related to the COPD component.