Impacts of extreme heat on emergency medical service calls in King County, Washington, 2007–2012: relative risk and time series analyses of basic and advanced life support

Abstract

BackgroundExposure to excessive heat kills more people than any other weather-related phenomenon, aggravates chronic diseases, and causes direct heat illness. Strong associations between extreme heat and health have been identified through increased mortality and hospitalizations and there is growing evidence demonstrating increased emergency department visits and demand for emergency medical services (EMS). The purpose of this study is to build on an existing regional assessment of mortality and hospitalizations by analyzing EMS demand associated with extreme heat, using calls as a health metric, in King County, Washington (WA), for a 6-year period.MethodsRelative-risk and time series analyses were used to characterize the association between heat and EMS calls for May 1 through September 30 of each year for 2007–2012. Two EMS categories, basic life support (BLS) and advanced life support (ALS), were analyzed for the effects of heat on health outcomes and transportation volume, stratified by age. Extreme heat was model-derived as the 95th (29.7 °C) and 99th (36.7 °C) percentile of average county-wide maximum daily humidex for BLS and ALS calls respectively.ResultsRelative-risk analyses revealed an 8 % (95 % CI: 6–9 %) increase in BLS calls, and a 14 % (95 % CI: 9–20 %) increase in ALS calls, on a heat day (29.7 and 36.7 °C humidex, respectively) versus a non-heat day for all ages, all causes. Time series analyses found a 6.6 % increase in BLS calls, and a 3.8 % increase in ALS calls, per unit-humidex increase above the optimum threshold, 40.7 and 39.7 °C humidex respectively. Increases in “no” and “any” transportation were found in both relative risk and time series analyses. Analysis by age category identified significant results for all age groups, with the 15–44 and 45–64 year old age groups showing some of the highest and most frequent increases across health conditions. Multiple specific health conditions were associated with increased risk of an EMS call including abdominal/genito-urinary, alcohol/drug, anaphylaxis/allergy, cardiovascular, metabolic/endocrine, diabetes, neurological, heat illness and dehydration, and psychological conditions.ConclusionsExtreme heat increases the risk of EMS calls in King County, WA, with effects demonstrated in relatively younger populations and more health conditions than those identified in previous analyses.

Hospitalizations for heat-stress illness varies between rural and urban areas: an analysis of Illinois data, 1987–2014

“…These studies have focused on a variety of outcomes impacted by heat, including cardiovascular disease, respiratory diseases, and asthma [25, 27–29]. Recent studies utilizing emergency dispatch data demonstrated that morbidity rates are strongly associated with temperature increases [30–32]. Among the elderly, emergency department visits and hospitalizations for a variety of health conditions are more frequent during extreme heat events [25, 33–35].…”

A Geographical Analysis of Emergency Medical Service Calls and Extreme Heat in King County, WA, USA (2007–2012)

“…There are many studies that have analyzed the relationship between extreme heat and morbidity and mortality; nearly all have concluded that extreme heat is associated with increased risk of death, hospitalizations, and other illnesses, especially illnesses related to the cardiovascular and respiratory systems [ 5 , 6 , 7 ]. Furthermore, researchers have observed increased emergency medical service call volumes during heat events [ 8 , 9 , 10 , 11 , 12 , 13 ]. Bassil et al [ 11 ] concluded, on average, there was a 16% increase in heat related illness calls for every one point increase in humidex.…”

“…Income level can affect the patient’s health status and ability to treat or manage pre-existing health conditions leaving them more susceptible to heat illness. For example, diabetes has a strong correlation with low income or poverty households [ 40 ] in addition to a strong correlation with extreme heat vulnerability [ 1 , 13 ]. Drug or alcohol use and the ability to seek help is another confounding factor correlated with both low socioeconomic status [ 22 ] and increased risk of an Emergency Medical Service (EMS) call in an extreme heat event [ 13 ].…”

“…As the most populous northern county in the Pacific Northwest and 13th in the United States, research indicates that King County in Washington State is vulnerable to the health impacts of increasing extreme heat events. Specifically, Calkins et al [ 13 ] found that in King County, WA, basic life support (BLS) calls increased by 8% on days exceeding a county-wide averaged maximum humidex above the 99th percentile (36.7 °C) and by 14% for advanced life support (ALS) calls on days exceeding a county-wide averaged maximum humidex above the 95th percentile (29.7 °C). Additionally, research from Busch Isaksen et al [ 5 , 6 ] demonstrated increased risk for mortality and hospitalizations across age groups and cause of deaths and admissions.…”

Quantitative Analysis of the Demand for Healthcare Services

“…Nowadays, when the demand for medical services is growing (Calkins et al, 2016;Eastwood et al, 2015;Veser et al, 2015;Williams, 2015) and the same trend is expected in the future, demand analysis has become an increasingly important area in every organization. On the other hand, due to serious financial difficulties in most of the countries, budgets became even more limited and reduced.…”