The Impact of Smoking History on Baseline Characteristic in Patients With Severe Asthma in the German Asthma Net (GAN).

BACKGROUND

Patients with asthma with >10 pack-years are frequently excluded from asthma trials. Little is known about how smoking affects their characteristics and therefore may impact treatment choices.

OBJECTIVE

To evaluate the impact of cumulative smoking history on the characteristics of patients with severe asthma.

METHODS

We analyzed pulmonary function tests, asthma control, exacerbation rate, and biomarkers. We compared active and ex-smokers (=ever-smokers) versus never-smokers and performed linear models for 3 groups stratified by smoking history (<10 pack-years [py], 10-20 py, and >20 py). Data were obtained from the severe asthma registry German Asthma Net.

RESULTS

We included 2478 patients: 65 (2.6%) active smokers, 1005 (40.6%) ex-smokers, and 1408 (56.8%) never-smokers. Of the 1070 ever-smokers, 529 patients (21.3%) had <10 py, 304 (12.3%) 10-20 py, and 237 (9.6%) >20 py. Cumulative smoking history was associated with worse asthma control (>20 py: Asthma Control Test -1.76 [-2.76; -0.77] points [P < .001]; mini-Asthma Quality of Life Questionnaire -0.31 [-0.53; -0.10] points [P = .004]), whereas exacerbation rate and maintenance oral corticosteroid (OCS) doses were similar (P = .13 and P = 1.0). Cumulative smoking history was associated with smoking-related lung injury, for example, diffusing capacity for carbon monoxide (-0.37 mmol/min/kPa for 10-20 py [P = .014], respectively, -0.92 for >20 py [P < .001]), but forced expiratory volume in 1 second (FEV1) and FEV1 reversibility were similar. Cumulative smoking history was furthermore associated with 0.84 [0.73; 0.97]-fold lower fractional exhaled nitric oxide (FeNO) concentrations (P = .007), whereas blood eosinophil count and IgE levels were comparable (BEC: P = 1.0 and IgE: P = .49).

CONCLUSIONS

Cumulative smoking history in patients with asthma is associated with worse disease control, lower FeNO levels, and smoking-related lung injuries. Despite these differences, key asthma characteristics such as BEC, IgE, OCS dose, and exacerbation rates remain similar. If thoroughly examined and selected, patients with >10 py may also qualify for targeted treatments.