The Acute Effects of Ambient Temperature Exposure on Mental Illness Related Emergency Room Visits in the City of Toronto

Abstract

Objectives: The purpose of this study was to assess the effects of extreme ambient temperature on hospital emergency room (ER) visits related to mental and behavior disorders in Toronto, Canada. Methods: A time series study was conducted using health and climatic data from April 1st 2002 to March 31st 2010. Relative risks for increases in ER visits were estimated for specific mental and behavior disorders (MBD) after exposure to hot and cold temperatures while using 50th percentile of the mean temperature distribution as the reference. The non-linear nature of the exposure–outcome relationship was accounted for using a distributed lag non-linear model (DLNM). The effects of seasonality, humidity, day of the week and outdoor air pollutants (CO2, O3, PM2.5, NO2, and SO2) were also adjusted. Results: We observed positive associations between elevated mean temperatures and hospital ER visits for MBD. For hot temperatures, significant increases in ER visits for MBD were observed after a mean temperature threshold of about 24°C. The association generally lasted about 3 to 4 lag days with the strongest effect occuring at lag 0 (RR = 1.06; 95% CI: 1.03 - 1.09). Similar trends and associations were observed for specific mental illnesses such as mood, neurotic, substance abuse, and schizophrenia related disorders. Cold temperature associations were only observed for schizophrenia. Conclusions: Our findings suggest that extreme temperature poses a risk to the health and wellbeing for individuals with mental and behavior disorders. Patient management and education may need to be improved as extreme temperatures become more prevalent.