Urban air pollution and emergency department visits related to central nervous system diseases, Toronto, Canada

Abstract

BACKGROUND AND AIM: Ambient air pollution has been associated with various adverse neurological health outcomes. This work comprehensively examined possible associations between concentration of five major urban air pollutants, two air quality indexes, and emergency department (ED) visits. METHODS: The analysis was done by sex, age group, and season for ED visits for central and peripheral nervous system diseases, in the period April 1, 2004-Decembr 31, 2015 (4,292 days in total). The study was done in Toronto, a Canadian megacity, using a case-crossover design. Conditional Poisson regression was realized to construct statistical models. Our focus was on daily ED visits covering all diseases of the nervous system and identified by ICD-10 codes (G00-G99). RESULTS:In the study period, 140,511 ED visits for diseases of the nervous system among Toronto residents were recorded: 83,602 (59.5%) for women and 56,909 (40.5%) for men. We found that nearly 64% of the considered ED visits were related to the episodic and paroxysmal disorders (G40-G47), with the majority of those visits related to migraines (39%). Based on a number of positive consistent associations, largest effect on ED visits for G40-G47, especially G43 (migraines) was among women exposed to ambient CO, especially with either immediate effect (0 and 1 lag) or a week long effect (6 and 7 lag) were found. Relative risks (RR) with 95% confidence intervals were reported for a one interquartile range (IQR) increase, (IQR=0.1 ppm). Women exposed to CO had RR of 1.036 (1.007-1.065) on the same day (especially older women), and 1.019 (1.004-1.033), 1.024 (1.010-1.039), and 1.022 (1.007-1.036) for lags 1, 6, and 7 days, respectively. CONCLUSIONS:Our findings support the associations between onset of possible diseases of the central nervous system (particularly migraines) and concentration of ambient CO, even at relatively low levels, detected in Toronto. KEYWORDS: acute exposure, ambient carbon monoxide, case-crossover, conditional Poisson, migraine, female