Evidence of the role of short-term exposure to ozone on ischaemic cerebral and cardiac events: the Dijon Vascular Project (DIVA).

OBJECTIVES: To confirm the effects of short-term exposure to ozone (O(3)) on ischaemic heart and cerebrovascular disease.
METHODS: Daily levels of urban O(3) pollution, the incidence of first-ever, recurrent, fatal and non-fatal ischaemic cerebrovascular events (ICVE) and myocardial infarction (MI) were correlated using a case-crossover design. The authors analysed 1574 ICVE and 913 MI that occurred in Dijon, France (150,000 inhabitants) from 2001 to 2007. Sulfur dioxide (SO(2)), nitrogen dioxide (NO(2)), carbon monoxide (CO) and particulate matter with an aerodiameter of ≤10 μg/m(3) (PM(10)) were used to create bi-pollutant models. Using the adjusted OR, the effects of O(3) exposure were calculated for every 10 μg/m(3) increase in pollutants in multivariate logistic models adjusted for temperature, humidity, flu outbreaks and holidays.
RESULTS: The authors found a significant association between exposure to O(3) and recurrent ICVE with a 3-day lag (OR=1.115; 95% CI 1.027 to 1.209). The direction and magnitude of the association between exposure to O(3) and recurrent MI were similar but not statistically significant. For incident events, the authors detected only a non-significant association for ICVE with a 2-day lag (OR=1.041; 95% CI 0.996 to 1.089). In the subgroup analysis for ICVE, the authors observed an increased association with cardiovascular risk factors (OR=1.523; 95% CI 1.149 to 2.018). For MI, the authors found an association with O(3) when hypercholesterolaemia was present (OR=1.111; 95% CI 1.020 to 1.211), and the association became stronger with the number of cardiovascular risk factors. The authors found a marked dose-response relationship.
CONCLUSION: Recurrent ICVE and MI could be triggered by short-term exposure to even low levels of O(3), especially among subjects with severe vascular risk factors.