Respiratory Impairment and Systemic Inflammation in Cedar Asthmatics Removed from Exposure

Background

Prior research has shown that removing occupational asthmatics from exposure does not routinely lead to significant improvements in respiratory impairment. These studies were of limited duration and factors determining recovery remain obscure. Our objective was to evaluate residual respiratory impairment and associated sputum and blood biomarkers in subjects with Western red cedar asthma after exposure cessation.

Methods

Subjects previously diagnosed with cedar asthma, and removed from exposure to cedar dust for at least one year, were recruited. Subjects completed a questionnaire and spirometry. PC₂₀ (methacholine concentration that produces 20% fall in FEV₁ (forced expiratory volume at 1 second)) sputum cellularity and select T_h1/T_h2 (T helper cells 1 and 2) cytokine concentrations in peripheral blood were determined. The asthma impairment class was determined and multivariate analyses were performed to determine its relationship with sputum cell counts and serum cytokines.

Results

40 non-smoking males (mean age 62) were examined at a mean interval of 25 years from cedar asthma diagnosis and 17 years from last cedar exposure. 40% were in impairment class 2/3. On average, the PC₂₀ had increased by 2.0 mg/ml; the FEV₁ decreased by 1.5 L, with greater decrease in those with greater impairment. Higher impairment was associated with serum interferon-gamma (mean = 1.3 pg/ml in class 2/3 versus 0.62 pg/ml in class 0/1, p = 0.04), mainly due to the FEV₁ component (correlation with interferon-gamma = −0.46, p = 0.005).

Conclusion

Years after exposure cessation, patients with Western red cedar asthma have persistent airflow obstruction and respiratory impairment, associated with systemic inflammation.