Small airway dysfunction in pneumoconiosis: a cross-sectional study.

Background: Although several histological studies have documented airway inflammation and remodelling in the small airways of dust-exposed workers, little is known regarding the prevalence and risk factors of small airway dysfunction (SAD) in pneumoconiosis. The present study investigated the prevalence and characteristics of spirometry-defined SAD in pneumoconiosis and assessed the risk factors for associated with SAD.

Methods: A total of 1255 patients with pneumoconiosis were invited to participate, of whom 1115 patients were eligible for final analysis. Spirometry was performed to assess SAD using the following three indicators: maximal mid-expiratory flow and forced expiratory flow 50% and 75%. SAD was defined as at least two of these three indicators being less than 65% of predicted value. Logistic regression analyses were used to analyse the relationships between clinical variables and SAD.

Results: Overall, 66.3% of patients with pneumoconiosis had SAD, among never-smokers the prevalence of SAD was 66.7%. The proportion of SAD did not differ among the subtypes of pneumoconiosis. In addition, SAD was present across the patients with all stages of pneumoconiosis. Even among those with forced expiratory volume in 1 s (FEV) ≥ 80% and FEV/forced vital capacity ratio ≥ 70%, 40.8% of patients had SAD. Patients with SAD were older than patients without SAD, more likely to be women and heavy smokers. Importantly, patients with SAD had more severe airflow obstruction, air trapping, and diffusion dysfunction. All patients with both pneumoconiosis and chronic obstructive pulmonary disease had SAD. Based on multivariate analysis, overall, aged 40 years and older, female sex, heavy smoking, body mass index ≥ 25.0 kg/m and pneumoconiosis stage III were significantly associated with increased risk of SAD. Among the never smokers, risk factors for SAD included female sex, BMI ≥ 25.0 kg/m, pneumoconiosis stage II and stage III CONCLUSION: Spirometry-defined SAD is one of the common functional abnormalities caused by occupational dust exposure and should be taken into account when monitoring respiratory health of workers to guide the early precautions and management in pneumoconiosis.