Background: Low-grade systemic inflammation is linked to abnormal spirometry. Impulse oscillometry (IOS) is sensitive in detecting peripheral airway dysfunction, but inflammation in relation to IOS is poorly studied.
 
Objective: To analyze associations between C-reactive protein (CRP), blood eosinophils (B-Eos), blood neutrophils (B-Neu), blood leukocytes (B-Leu) and IOS.
 
Methods: Blood biomarkers and IOS were assessed in 10602 adults (50-65 years) within the Swedish CardioPulmonary bioImage Study. Upper tertiles for CRP (>1.8 mg/L), B-Eos (>0.2 10⁹/L), B-Neu (>3.4 10⁹/L), B-Leu (>6.1 10⁹/L) were analyzed in relation to higher R₅, R₂₀, AX and f_res (>95^th percentile) or lower X₅ (<5^th percentile), based on healthy, never-smoking subjects.
 
Results: Median (interquartile range) levels of CRP, B-Eos, B-Neu, B-Leu were 1.1 (1.8) mg/L, 0.2 (0.1) 10⁹/L, 2.9 (1.3) 10⁹/L and 5.5 (1.9) 10⁹/L. Abnormal IOS was observed in 1715 (16%), of which 580 (34%) also had abnormal spirometry. Having several biomarkers in the upper tertile (1, 2 or 3-4 vs 0) was overall associated with abnormal IOS (Figure 1). Furthermore, having 2 or more biomarkers vs 0 in the upper tertile was linked to abnormal IOS in subjects with normal spirometry: adjusted odds ratios (95% confidence intervals) ranging from 1.3 (1.0, 1.6) to 1.6 (1.2, 2.1).

Conclusions:Low-grade systemic inflammation was related to abnormal IOS and appears to be consistent even when subjects had normal spirometry.