Heavy smoking among asthmatics tied to severe obstructive impairments
Among patients with asthma, heavy smoking appears to be an important risk factor for airflow reduction and fixed airflow obstruction, steroid insensitivity and specific comorbidities, but less allergy along with low fractional exhaled nitric oxide (FeNO) and blood eosinophils, according to a study.
The study included 521 asthmatic patients, among whom 294 were never smokers (0 pack-years [PY]), 104 were light smokers (1–10 PY), and 123 were heavy smokers (>10 PY). Researchers assessed demographic, clinical/functional, and biological parameters.
In the cohort, the heavy smokers were more likely to be older, male, overweight, and nonallergic. Although inhaled corticosteroid (ICS) dose and disease severity were similar among groups, heavy smoking was strongly associated with significant airflow limitation (mean FEV1/FVC, 0.65; p<0.01; mean FEV1%pred, 79.20; p<0.01), air trapping (mean RV%pred, 135.6; p<0.05; mean RV/TLC, 0.48; p<0.05), and fixed airflow obstruction (postbronchodilation FEV1/FVC, 0.66; p=0.01) as compared with never and light smoking.
Heavy smokers exhibited reduced blood eosinophils (p<0.05) and FeNO (p<0.01), increased frequency of type-2 low inflammation, and long acting beta agonists/long acting muscarinic antagonists use, although they had a lower frequency of persistent rhinitis and chronic rhinosinusitis with nasal polyposis. This group of asthmatics also had a higher prevalence of paraseptal/bullous emphysema and arterial hypertension.
Risk assessment of lung function impairment revealed that heavy smoking was associated with lower odds of having allergy (odds ratio [OR], 0.5), persistent rhinitis (OR, 0.6), chronic rhinosinusitis with nasal polyposis (OR, 0.3), or high FeNO (OR, 0.4), but a higher likelihood of having fixed airflow obstruction (postbronchodilation FEV1%pred<80%: OR, 2.0; and postbronchodilation FEV1/FVC≤0.70, OR, 2.0).
The present data suggest that heavy smokers with asthma may represent a definite clinical phenotype.