Student Research: Miriam Calkins

Impact of Extreme Heat on Emergency Medical Services in King County, WA
Exposure Sciences (ES)
Faculty Advisor: 


Background: Climate change is projected to have serious long-term consequences for public health. The existing body of literature has largely characterized increases in hospitalization and mortality in relation to extreme heat, but limited research exists characterizing the relationship between extreme heat and emergency medical services (EMS).

Objective: The primary objective of this research was to assess the impact of extreme heat on health and county resources through the use of high definition meteorological data and EMS call data for King County, WA.

Methods: Using EMS records and high-resolution meteorological data for 2007 through 2012, relative risk and time series analyses were conducted for the potential association between extreme heat and EMS calls. Extreme heat was defined as the 95th percentile of average daily county-wide maximum humidex values for Basic Life Support (BLS) EMS response data and the 99th percentile for Advanced Life Support (ALS) EMS response data. The analysis focused on health outcomes and level of transportation for all ages as well as six age categories and assessed for duration and cool down effects. Additional analyses of the impacts on cost were conducted.

Results: For all ages, all causes, there was an 8% increase in BLS calls on a 95th percentile heat day (29.7 °C) compared to a non-heat day and a 14% increase in ALS calls on a 99th percentile heat day (36.7 °C) compared to a non heat day. The time series analyses demonstrated a 6.6% increase in BLS calls per degree increase above the statistically optimal threshold of 40.7 °C humidex and a 3.8% increase in ALS calls per degree increase above the optimal threshold of 39.7 °C humidex. Analysis by age category consistently identified significant results in 15-44 and 45-64 year olds, although 0-4 year olds and 65+ age groups also contained significant increases in risk for some health outcomes.
Conclusions: This research captured the volume of cases that may not be serious enough to warrant hospitalization, but still demand significant county resources, using EMS calls as a surrogate for adverse health outcomes. All-ages increases in risk and age-specific health effects were consistent with the limited existing research on EMS calls and heat, however the presence of increases in risk for relatively young populations was markedly different from regional effects demonstrated in more severe health metrics.