Air pollution and humidity as triggering factors for stroke. Results of a 12-year analysis in the West Paris area

Abstract Background and Purpose Previous studies have suggested an association between stroke and meteorological factors, air pollution and acute respiratory infections as triggering factors. Often, these factors have been evaluated separately. We evaluated the association between all these environmental triggering factors and calls for suspectedstroke in a suburb in west Paris from 2004 to 2015. Methods We used data from the emergency medical dispatchingcenter of all calls for suspectedstroke (SAMU 78), climatic parameters (MeteoFrance), pollution (AIRPARIF), and data from influenza epidemic surveillance networks ( GROGand Sentinelles). The association between short-term exposure (1-day lag) to environmental triggering factors and stroke occurrence was analyzed using negative-binomial log linear regression model for counting time series. Results Between 2004 and 2015, a total of 11,037 calls for suspectedstroke were recorded. In bivariate analysis, there were associations between calls for suspectedstroke and temperature (mean, maximum and minimum), humidity and influenza epidemic. In multivariable analysis, only two variables were associated with calls for suspectedstroke: humidity [3.93% excess relative risk(ERR) of stroke per 10% increase in humidity; 95% confidence interval (CI), 1.42 to 6.51; P P = 0.002). Conclusions This study suggests that short-term exposure to air pollution and a high level of humidity are associated with a significant excess relative riskof calls for suspectedstroke.