A Nationwide Study of Particulate Matter and Daily Hospitalizations for Respiratory Diseases in Italy

Introduction: The relationship between air pollution and respiratory morbidity has been widely addressed in urban and metropolitan areas but little is known about the effects in non-urban settings. Aims: To assess the short-term effects of PM10 and PM2.5 on respiratory admissions in whole country of Italy during 2006-2015. Methods: We estimated daily PM concentrations at the municipality level (n 8,092) using a machine learning method based on satellite data and spatiotemporal predictors. We collected daily counts of respiratory hospital admissions for each Italian municipality. We considered five different outcomes: all respiratory, asthma, chronic obstructive pulmonary disease (COPD), lower and upper respiratory tract infections (LRTI and URTI). We ran municipality-specific time-series models and we meta-analyzed individual effects to obtain national estimates for the above outcomes. Finally, we tested for effect modification by sex, age classes and degree of urbanization. Results: A total of 4,154,887 non-scheduled acute respiratory admission were registered during 2006-2015, of which 29%, 12%, 6%, and 3% were for LRTI, COPD, URTI and asthma, respectively. Daily mean PM10 and PM2.5 concentrations over the study period were 23.3 and 17 mg/m3. For each 10 mg/m3 increases in PM10 and PM2.5 at lag 0-5 days, we found excess risks of total respiratory diseases equal to 1.10% (95% confidence intervals: 0.82, 1.39) and 0.82 (0.35, 1.30), respectively. Higher effects were found in the elderly and in areas less urbanized. Conclusions: Short-term exposure to PM is harmful for the respiratory system, especially in elderly patients. Strong effects were found also in rural areas.