title: 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: BACKGROUND
  Exposure 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.
  
  
  METHODS
  Relative-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.
  
  
  RESULTS
  Relative-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.
  
  
  CONCLUSIONS
  Extreme 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.
authors.affiliation: Department of Environmental and Occupational Health Sciences, School of Public Health, University of Washington, 1959 NE Pacific St., P.O. Box 237234, Seattle, WA, 98195, USA. miriac@uw.edu.
authors.forename: Miriam M
authors.initials: MM
authors.lastname: Calkins
authors.affiliation: Department of Environmental and Occupational Health Sciences, School of Public Health, University of Washington, 1959 NE Pacific St., P.O. Box 237234, Seattle, WA, 98195, USA. tania@uw.edu.
authors.forename: Tania Busch
authors.initials: TB
authors.lastname: Isaksen
authors.affiliation: Emergency Medical Services Division, Seattle and King County Department of Public Health, 401 5th Ave, Suite 1200, Seattle, WA, 98104, USA. benjamin.stubbs@kingcounty.gov.
authors.forename: Benjamin A
authors.initials: BA
authors.lastname: Stubbs
authors.affiliation: Department of Environmental and Occupational Health Sciences, School of Public Health, University of Washington, 1959 NE Pacific St., P.O. Box 237234, Seattle, WA, 98195, USA. airion@uw.edu.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Yost
authors.affiliation: Department of Environmental and Occupational Health Sciences, School of Public Health, University of Washington, 1959 NE Pacific St., P.O. Box 237234, Seattle, WA, 98195, USA. rfenske@uw.edu.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Fenske
mesh_terms: D000293:Adolescent; D000328:Adult; D022561:Advanced Cardiac Life Support / Q000706:statistics & numerical data*; D017677:Age Distribution; D000368:Aged; D002648:Child; D002980:Climate; D004632:Emergency Medical Services / Q000706:statistics & numerical data*; D018882:Heat Stress Disorders / Q000453:epidemiology* / Q000628:therapy*; D006358:Hot Temperature / Q000009:adverse effects*; D006801:Humans; D008875:Middle Aged; D018570:Risk Assessment / Q000706:statistics & numerical data; D012307:Risk Factors; D014861:Washington; D055815:Young Adult
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