Associations of traffic related air pollutants with hospitalisation for first acute myocardial infarction: the HEAPSS study

Background: Acute myocardial infarction (AMI) is the leading cause of death attributed to cardiovascular diseases. An association between traffic related air pollution and AMI has been suggested, but the evidence is still limited. Objectives: To evaluate in a multicentre study association between hospitalisation for first AMI and daily levels of traffic related air pollution. Methods: The authors collected data on first AMI hospitalisations in five European cities. AMI registers were available in Augsburg and Barcelona; hospital discharge registers (HDRs) were used in Helsinki, Rome and Stockholm. NO2, CO, PM10 (particles < 10 mu m), and O-3 were measured at central monitoring sites. Particle number concentration (PNC), a proxy for ultrafine particles (< 0.1 mu m), was measured for a year in each centre, and then modelled retrospectively for the whole study period. Generalised additive models were used for statistical analyses. Age and 28 day fatality and season were considered as potential effect modifiers in the three HDR centres. Results: Nearly 27 000 cases of first AMI were recorded. There was a suggestion of an association of the same day CO and PNC levels with AMI: RR = 1.005 (95% CI 1.000 to 1.010) per 0.2 mg/m(3) and RR = 1.005 (95% CI 0.996 to 1.015) per 10000 particles/cm(3), respectively. However, associations were only observed in the three cities with HDR, where power for city-specific analyses was higher. The authors observed in these cities the most consistent associations among fatal cases aged < 75 years: RR at 1 day lag for CO = 1.021 (95% CI 1.000 to 1.048) per 0.2 mg/m(3), for PNC = 1.058 (95% CI 1.012 to 1.107) per 10000 particles/cm(3), and for NO2 = 1.032 (95% CI 0.998 to 1.066) per 8 mu g/m(3). Effects of air pollution were more pronounced during the warm than the cold season. Conclusions: The authors found support for the hypothesis that exposure to traffic related air pollution increases the risk of AMI. Most consistent associations were observed among fatal cases aged < 75 years and in the warm season.