A15-04 Airway-to-Lung Volume Ratio and Incidence of Interstitial Lung Abnormality in Community-dwelling Adults: The Multi-Ethnic Study of Atherosclerosis (MESA)

Abstract Rationale We have previously demonstrated cross-sectional associations between larger CT-assessed airway-to-lung volume ratio (ALVR) and increased odds of interstitial lung abnormality (ILA). Whether ALVR is associated with incident ILA is unknown. Methods The Multi-Ethnic Study of Atherosclerosis (MESA) is a prospective cohort of middle-aged and older community-dwelling US adults. All participants underwent cardiac CT scans at exam 1; a subset had repeat cardiac CT scans at exams 2-5. ALVR was quantified on exam 1 scans as the mean of airway lumen diameters measured at 19 standard anatomic locations from trachea to subsegment divided by the cube root of total lung volume. ILA were defined as nondependent abnormalities involving 5% of a lung zone, including ground-glass, reticular abnormalities, honeycombing, and traction bronchiectasis. Participants with ILA at exam 1, who were unable to have ALVR calculated, or who did not have serial imaging were excluded. ILA incidence rates were calculated as the number of new cases divided by the total person-years at risk. Cox proportional hazards models were used to estimate hazard ratios (HR) for incident ILA, adjusting for age, gender, race/ethnicity, cigarette smoking status, cigarette pack-years, body mass index, and imaged lung volume. Poisson regression models offset for log-transformed person-years were used to estimate incidence rate ratios (IRRs) for incident ILA using the same covariates. Results Among 5,182 participants (52% female, mean±SD age of 61.4±10.0 years, 41% White, 27% Black, 20% Hispanic, 49% ever smokers), 249 developed incident ILA over median follow-up of 3.2 (range 1.1-11.3) years, corresponding to an overall incidence rate of 12.5 per 1,000 person-years. Kaplan-Meier curves stratified by ALVR quartiles showed greater cumulative incidence of ILA across increasing ALVR quartiles. In Cox proportional hazards and Poisson regression models accounting for person-years of follow-up, there were significant per-quartile trends in hazard ratios (HR per quartile 1.19, 95% CI 1.06-1.33, p = 0.003) and incidence rate ratios (IRR per quartile 1.15, 95% CI 1.03-1.29, p = 0.013) for incident ILA (Table). In sensitivity analysis using mean airway lumen diameter (the ALVR numerator) as the predictor, there remained significant per quartile trends for incident ILA (HR per quartile 1.18, 95% CI 1.05-1.33, p = 0.005; IRR per quartile 1.15, 95% CI 1.03-1.29, p = 0.017).Conclusion Higher baseline ALVR and mean airway diameter are associated with increased risk and incidence rate of ILA, suggesting that abnormalities in airway structure independent of total lung volume are an early event in the pathogenesis of pulmonary fibrosis. This abstract is funded by: NHLBI