Impact of smoking on asthma control with extrafine beclomethasone/formoterol: post hoc analysis of a prospective cohort study.

Objective: Exposure to tobacco smoke is a major risk factor for poor asthma control. We aimed to assess the response to asthma treatment based on patients' smoking status.

Methods: This post hoc analysis used data from a large prospective asthma cohort treated with inhaled extrafine beclomethasone/formoterol. Patients were retrospectively categorized as current smokers, former smokers, or nonsmokers. Asthma control and symptom severity were evaluated over 6 months using Global Initiative for Asthma (GINA) criteria. The primary outcome was the proportion of patients who achieved an improved GINA category of asthma control, while the secondary outcome was the proportion with well-controlled asthma. To account for baseline differences, the cohorts were propensity score-matched (1:1:1) based on age, sex, body mass index, self-reported physical activity, education level, and FEV₁.

Results: From an initial cohort of 17 098 patients, a matched sample of 2856 (952 per group) was selected, ensuring comparable baseline characteristics. After 6 months, an improved GINA category was observed in 78% of current smokers, 75% of former smokers, and 77% of nonsmokers (p = 0.381). The rates of well-controlled asthma were comparable across groups (current smokers: 58%, former smokers: 54%; nonsmokers: 57%, p = 0.255). Uncontrolled asthma remained infrequent but was more prevalent in current (10%) and former (8.9%) smokers than in nonsmokers (5.7%) (p = 0.002 and p = 0.033, respectively).

Conclusions: Asthma patients, regardless of smoking status, demonstrate a similar response to treatment. Uncontrolled asthma, though rare under treatment, is more common among smokers, due to their higher baseline severity.