Air pollution exposure is associated with restrictive rather than obstructive ventilatory patterns

Abstract

Background Ambient air pollutants have been associated with lower FVC and FEV₁ levels, with effect estimates mostly being larger for FVC than for FEV₁. We assessed for the first time explicitly whether air pollution exposure is associated with obstructive or restrictive ventilatory patterns.

Methods The residential address of subjects of the LifeLines cohort study was geocoded and annual average exposure to NO₂, PM_2.5, PM₁₀ and PM_2.5 absorbance estimated using land use regression models from the ESCAPE study. We used adjusted linear regression models to assess associations of air pollutants with pre-bronchodilator FEV₁, FVC and FEV₁/FVC in n=51,855 subjects.

Results Exposure to NO₂, PM₁₀ and PM_2.5 absorbance showed consistent significant associations with lower levels of FVC, but not with FEV₁. Since the estimated effects were smaller for FEV₁ than for FVC, this resulted in positive associations with their ratio (FEV₁/FVC). Statified analysis suggested that associations between PM₁₀, PM_2.5 absorbance and FVC were stronger in females, subjects with overweight, asthma, and airway obstruction, yet without significant interactions.

Conclusions Ambient air pollution exposure is associated with restrictive rather than obstructive ventilatory patterns. This may reflect pulmonary fibrosis, a disease which has, thus far, largely been understudied in relation to air pollution exposure in large scale epidemiological studies (Johannson, K.A. et al. Chest, 2015;147:1161-1167). Identifying susceptible subgroups may help to set exposure limits and pinpoint potential biological mechanisms underlying observed associations, which will render further studies in experimental settings.