Seasonal effect of PM_2.5 exposure in patients with COPD: a multicentre panel study

Background: Exposure to particulate matter <2.5 microm (PM_2.5) is linked to chronic obstructive pulmonary disease (COPD), but most studies lack individual PM_2.5 measurements. Seasonal variation and their impact on clinical outcomes remain understudied. Objective: This study investigated the impact of PM_2.5 concentrations on COPD-related clinical outcomes and their seasonal changes. Methods: A multicentre panel study enrolled 105 COPD patients (age range: 46-82) from July 2019 to August 2020. Their mean forced expiratory volume in 1 second after bronchodilation was 53.9%. Individual PM_2.5 levels were monitored continuously with indoor measurements at residences and outdoor data from the National Ambient Air Quality Monitoring Information System. Clinical parameters, including pulmonary function tests, symptom questionnaires (CAT and SGRQ-C), and impulse oscillometry (IOS), were assessed every three months over the course of one year. Statistical analysis was conducted using a linear mixed-effect model to account for repeated measurements and control for confounding variables, including age, sex, smoking status and socioeconomic status. Results: The mean indoor and outdoor PM_2.5 concentrations were 16.2 ± 8.4 microg m^-3 and 17.2 ± 5.0 microg m^-3, respectively. Winter had the highest PM_2.5 concentrations (indoor, 18.8 ± 11.7 microg m³; outdoor, 22.5 ± 5.0 microg m^-3). Higher PM_2.5 concentrations significantly correlated with poorer St. George's Respiratory Questionnaire for COPD (SGRQ-C) scores and increased acute exacerbations, particularly in winter. Patients of lower socioeconomic status were more vulnerable. Increased PM_2.5 concentrations were also associated with amplified small airway resistance (R5-R20). Conclusions: PM_2.5 concentration changes are positively correlated with poorer SGRQ-C scores and increased acute exacerbations in COPD patients with significant seasonal variations, especially in winter.