A case-crossover analysis of out-of-hospital coronary deaths and air pollution in Rome, Italy

Rationale: Out-of-hospital coronary heart disease death is a major public health problem, but the association with air pollution is not well understood. Objectives: We evaluated the association between daily ambient air pollution levels (particle number concentration [PNC]-a proxy for ultrafine particles [diameter < 0.1 mu m], mass of particles with diameter less than 10 mu m [PM10]; CO, NO2, and O-3) and the occurrence of fatal, nonhospitalized coronary events. Methods: Subjects were 5,144 out-of-hospital fatalities (410-414, International Classification of Diseases-9; 1998-2000) who had been residents of Rome. Hospitalizations during the 3 yr before death were considered to identify comorbidities (e.g., diabetes, hypertension, heart failure, dysrhythmia, chronic obstructive pulmonary disease). Statistical analyses were performed using a case-crossover design. Measurements and Main Results: The association with out-of-hospital coronary deaths was statistically significant for PNC, PM10, and CO. Air pollution on the day of death had the strongest effect (e.g., 7.6% increase [95% confidence interval, 2.0-13.6%]) for an interquartile range of PNC, 27,790 particles/cm(3). The 65-74- and 75+-yr age groups were at higher risk than the 35-64-yr age group, and there was a suggestion of effect modification for people with hypertension and chronic obstructive pulmonary disease. Conclusions: Air pollutants originating from combustion processes, including ultrafine particles, are related to fatal, nonhospitalized coronary events. The effect is stronger among people over 65 years of age, but is not limited to a group with a specific comorbidity.