Airborne pollutants and lacunar stroke: a case cross-over analysis on stroke unit admissions

Particulate air pollution is known to be associated with cardiovascular disease. The relation of particulate air pollution with cerebrovascular disease (CVD) has not been extensively studied, particularly in relation to different subtypes of stroke. A time-series study was conducted to evaluate the association between daily air pollution and acute stroke unit hospitalizations in Mantua, Italy. We analyzed 781 CVD consecutive patients living in Mantua county admitted between 2006–08. Data on stroke types, demographic variables, risk factors were available from the Lombardia Stroke Registry. Daily mean value of particulate matter with a diameter <10 µm (PM(10)), carbon monoxide, nitric oxide, nitrogen dioxide, sulphur dioxide, benzene and ozone were used in the analysis. The association between CVD, ischemic strokes subtypes and pollutants was investigated with a case-crossover design, using conditional logistic regression analysis, adjusting for temperature, humidity, barometric pressure and holidays. Among the 781 subjects admitted 75.7% had ischemic stroke, 11.7% haemorrhagic stroke 12.6% transient ischemic attack. In men admission for stroke was associated with PM(10) [odds ratio (OR) 1.01, 95%; confidence interval (CI) 1.00–1.02; P<0.05]. According to the clinical classification, lacunar anterior circulation syndrome stroke type was related to PM(10) level registered on the day of admission for both genders (OR: 1.01, 95%; CI: 1.00–1.02; P<0.05) while for total anterior circulation syndrome stroke only in men (OR: 1.04, 95%; CI 1.01–1.07; P<0.05). In conclusion, our study confirms that air pollution peaks may contribute to increase the risk of hospitalization for stroke and particulate matter seems to be a significant risk factor, especially for lacunar stroke.