Air Pollution Exposure and Daily Lung Function in Chronic Obstructive Pulmonary Disease: Effect Modification by Eosinophil Level
Lina Nurhussien, Choong‐Min Kang, Petros Koutrakis, Brent A. Coull, Mary B. Rice
Abstract
Abstract Rationale Few studies have assessed personal exposure to pollutants and lung function among adults with chronic obstructive pulmonary disease (COPD). Blood eosinophil level may be a biomarker of airway inflammation and pollution susceptibility. Objectives To evaluate if daily pollutant exposures are associated with lung function and if associations are modified by eosinophil level in COPD. Methods We recruited 30 former smokers with moderate to severe COPD living in the Boston area and followed them for up to 4 nonconsecutive months in different seasons. Participants measured morning lung function and carried a portable air quality monitor daily. Previous-day exposure to pollutants (particulate matter ⩽2.5 μm in aerodynamic diameter, nitrogen dioxide [NO2], and ozone) were measured by portable and community monitors. We constructed multilevel linear mixed-effects models with random intercepts for person and observation month, adjusted for temperature, humidity, age, sex, race, height, weight, income, and season, to assess associations of previous-day pollutant exposure with lung function and effect modification by eosinophil count (<150/μl vs. ⩾150/μl). Results A total of 3,314 observations with exposure and lung function data were collected. Each interquartile range (5.1 parts per billion [ppb])–higher previous-day personal exposure to NO2 was associated with an 11.3 ml (95% confidence interval [CI], −18.7 to −4.0) lower forced expiratory volume in 1 second (FEV1) and an 18.0 ml (95% CI, −32.0 to −4.2) lower forced vital capacity. Personal and community-level exposure to particulate matter ⩽2.5 μm in aerodynamic diameter and community-level NO2 were negatively associated with FEV1 among the 55.2% of participants with the higher eosinophil level (P interaction < 0.05). Conclusions Our study highlights the need to address air pollution exposure among patients with COPD. Future research is needed to verify if eosinophil level is a biomarker for susceptibility to air pollution in COPD.