New Study: Impact of Ontario’s Harmonized Heat Warning and Information System on emergency department visits for heat-related illness in Ontario, Canada: a population-based time series analysis

• Post by: Olivia Teresa Caruso
• 2:40PM Sep 14, 2022
• No Comment

A team of researchers led by Kristin K Clemens with Alexandra M Ouédraogo, Britney Le, James Voogt, Melissa MacDonald, Rebecca Stranberg, Justin W Yan, E Scott Krayenhoff, Jason Gilliland, Cheryl Forchuk, Rafique Van Uum, and Salimah Z Shariff recently published an article entitled: “Impact of Ontario’s Harmonized Heat Warning and Information System on emergency department visits for heat-related illness in Ontario, Canada: a population-based time series analysis.”

Ontario’s Harmonized Heat Warning and Information System (HWIS) brings harmonized, regional heat warnings and standard heat-health messaging to provincial public health units prior to periods of extreme heat.

The researchers aimed to determine whether the implementation of the harmonized HWIS in May 2016 was associated with a reduction in emergency department (ED) visits for heat-related illness in urban locations across Ontario, Canada

They conducted a population-based interrupted time series analysis from April 30 to September 30, 2012–2018, using administrative health and outdoor temperature data. We used autoregressive integrated moving average models to examine whether ED rates changed following implementation of the harmonized HWIS, adjusted for maximum daily temperature. They also examined whether effects differed in heat-vulnerable groups (≥65 years or <18 years, those with comorbidities, those with a recent history of homelessness), and by heat warning region.

Over the study period, heat alerts became more frequent in urban areas (6 events triggered between 2013 and 2015 and 14 events between 2016 and 2018 in Toronto, for example). The mean rate of ED visits was 47.5 per 100,000 Ontarians (range 39.7–60.1) per 2-week study interval, with peaks from June to July each year. ED rates were particularly high in those with a recent history of homelessness (mean rate 337.0 per 100,000). Although rates appeared to decline following implementation of HWIS in some subpopulations, the change was not statistically significant at a population level (rate 0.04, 95% CI: −0.03 to 0.1, p=0.278).

In urban areas across Ontario, ED encounters for heat-related illness may have declined in some subpopulations following HWIS, but the change was not statistically significant. Efforts to continually improve HWIS processes are important given our changing Canadian climate.

Citation: Kristin K Clemens with Alexandra M Ouédraogo, Britney Le, James Voogt, Melissa MacDonald, Rebecca Stranberg, Justin W Yan, E Scott Krayenhoff, Jason Gilliland, Cheryl Forchuk, Rafique Van Uum, and Salimah Z Shariff. “Impact of Ontario’s Harmonized Heat Warning and Information System on emergency department visits for heat-related illness in Ontario, Canada: a population-based time series analysis.” Canadian Journal of Public Health, 1-12 (2022); https://doi.org/10.17269/s41997-022-00665-1