Changes in patient characteristics and patterns of visits to emergency departments during an extreme heat event

Abstract An extreme heat event (EHE) occurred in Western North America in late June 2021. Multiple studies in British Columbia, Canada, found significant impacts on mortality from this EHE, with less focus on morbidity to date. This study aims to examine changes in volumes and patterns of emergency department (ED) visits during the EHE. We compared 33 309 adult ED visits during the EHE with 116 367 visits on the same calendar days of four previous years (2016–2019) for 27 EDs across the province. We used descriptive analyses and conditional logistic regression to assess differences in patient demographics, pre-existing chronic diseases, visit acuity, presenting complaint, and visit outcome. On average, there were 528 (15%) more daily visits during the EHE than during the baseline, with larger increases among older adults and high acuity visits. Increases were observed in all EDs across the province, but smaller EDs with lower capacity had the largest relative increases. Significant increases in presenting complaints were observed for ear-related, cardiovascular and neurologic conditions, and patients leaving before triage. Among high acuity visits, there was a 15.6% increase for neurologic conditions, primarily due to altered level of consciousness. People with parkinsonism, chronic kidney disease, mood and anxiety disorders, and diabetes were more likely to visit the ED during the EHE. We found substantial changes in patient volumes and cause-specific patterns of ED visits during the 2021 EHE. These results can help inform planning for ED surges, and preparation in community and the broader health system to protect public health.