Air pollution enhance the progression of restrictive lung function impairment and diffusion capacity reduction: an elderly cohort study

Background: Some evidences have shown the association between air pollution exposure and the development of interstitial lung diseases. However, the effect of air pollution on the progression of restrictive ventilatory impairment and diffusion capacity reduction is unknown. This study aimed to evaluate the effects of long-term exposure to ambient air pollution on the change rates of total lung capacity, residual volume, and diffusion capacity among the elderly. Methods: From 2016 to 2018, single-breath helium dilution with the diffusion capacity of carbon monoxide was performed once per year on 543 elderly individuals. Monthly concentrations of ambient fine particulate matters (PM_2.5) and nitric dioxide (NO₂) at the individual residential address were estimated using a hybrid Kriging/Land-use regression model. Linear mixed models were used to evaluate the association between long-term (12 months) exposure to air pollution and lung function with adjustment for potential covariates, including basic characteristics, indoor air pollution (second-hand smoke, cooking fume, and incense burning), physician diagnosed diseases (asthma and chronic airway diseases), dusty job history, and short-term (lag one month) air pollution exposure. Results: An interquartile range (5.37 ppb) increase in long-term exposure to NO₂ was associated with an additional rate of decline in total lung volume (− 1.8% per year, 95% CI: − 2.8 to − 0.9%), residual volume (− 3.3% per year, 95% CI: − 5.0 to − 1.6%), ratio of residual volume to total lung volume (− 1.6% per year, 95% CI: − 2.6 to − 0.5%), and diffusion capacity (− 1.1% per year, 95% CI: − 2.0 to − 0.2%). There is no effect on the transfer factor (ratio of diffusion capacity to alveolar volume). The effect of NO₂ remained robust after adjustment for PM_2.5 exposure. Conclusions: Long-term exposure to ambient NO₂ is associated with an accelerated decline in static lung volume and diffusion capacity in the elderly. NO₂ related air pollution may be a risk factor for restrictive lung disorders.