Ambient, Indoor Air Pollution Exposures and Mild Chronic Obstructive Pulmonary Disease Trajectories in Non-Hospitalized Volunteers in Turin, Italy

Urban air pollution is a key driver of adverse respiratory outcomes, yet its precise impact on lung function trajectories in non-hospitalized patients with mild chronic obstructive pulmonary disease (COPD) has not been fully characterized. Objectives: This study investigated the complex interplay between ambient particulate matter exposure, residential microenvironmental factors, sociodemographic characteristics, and 1-year longitudinal lung function in mild COPD patients. Methods: A 1-year prospective cohort study was conducted on 50 non-hospitalized male volunteers residing in Turin (Italy) for a minimum of 5 consecutive years. Longitudinal lung function was assessed monthly via spirometric parameters, including forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), and the FEV1/FVC ratio. Ambient PM concentrations assigned according to residential location (PM2.5 and PM10) were integrated with a comprehensive residential microenvironmental and lifestyle profiling. To assess longitudinal changes in lung function while controlling for covariates, a Multivariate Analysis of Covariance (MANCOVA) was applied to estimate the simultaneous effects of these predictors on the joint lung function parameters over time. To fully account for the nested, repeated-measures structure of the dataset, linear mixed-effects models (LMMs) were deployed to calculate specific rates of functional decline over the 12 monthly intervals. This model assessed multiple exposure variables, including cooking appliances (gas vs. electric), domestic heating systems (internal vs. external boilers), smoking status, traffic exposure, and pets. Statistical associations were modeled using Principal Component Analysis (PCA) and Agglomerative Hierarchical Clustering (AHC). Results: The MANCOVA revealed a highly significant overall multivariate effect of the combined predictors on the joint lung function parameters (Wilks’ λ = 0.125, p < 0.001). Specifically, monthly PM2.5 concentrations (p = 0.001), residential proximity to primary roads (p = 0.004), and the utilization of gas-fueled cooking appliances (p = 0.002) exerted statistically significant independent effects on the decline in the spirometric profile, whereas PM10 and internal boilers did not (p > 0.05). PCA then identified four significant components explaining 88.8% of the total variance, demonstrating collinearity between ambient PM2.5 and PM10 concentrations and revealing that spatial residential distribution significantly accounts for the longitudinal variability in FEV1 and FVC. Furthermore, AHC successfully identified distinct patient clusters, confirming that indoor microenvironmental factors—predominantly the utilization of gas-fueled cooking stoves and internal boilers—could act as critical compounding risk factors alongside outdoor traffic pollution. Conclusions: These preliminary findings suggest how intersecting urban outdoor pollutants and specific household factors may potentially contribute to the trajectories of mild COPD. These data underscore the potential benefit of integrated environmental-indoor risk assessment methodologies and may inform future targeted public health interventions and preventive strategies to mitigate exacerbations in vulnerable urban populations.