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 suspected stroke in a suburb in west Paris from 2004 to 2015.

We used data from the emergency medical dispatching center of all calls for suspected stroke (SAMU 78), climatic parameters (MétéoFrance), pollution (AIRPARIF), and data from influenza epidemic surveillance networks (GROG and 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.

Between 2004 and 2015, a total of 11,037 calls for suspected stroke were recorded. In bivariate analysis, there were associations between calls for suspected stroke and temperature (mean, maximum and minimum), humidity and influenza epidemic. In multivariable analysis, only two variables were associated with calls for suspected stroke: humidity [3.93% excess relative risk (ERR) of stroke per 10% increase in humidity; 95% confidence interval (CI), 1.42 to 6.51; P<0.002] and pollution on the “Air Parif Atmo” scale (2.86% ERR of stroke per 1 unit increase; 95% CI, 1.01 to 4.75; P=0.002).

This study suggests that short-term exposure to air pollution and a high level of humidity are associated with a significant excess relative risk of calls for suspected stroke.