title: Short-term departures from an optimum ambient temperature are associated with increased risk of out-of-hospital cardiac arrest.
abstract: Associations have been reported between daily ambient temperature and all-cause and cardiovascular mortality. However, the potential harmful effect of temperature on out-of-hospital cardiac arrest (OHCA) is insufficiently studied.
  
  
  
  The objective of this study was to investigate the short-term association between ambient temperature and the occurrence of OHCA.
  
  
  
  In 5961 cases of OHCAs treated by Emergency Medical Service occurring in Stockholm County we investigated the association between the preceding 24-h and 1h mean ambient temperature, obtained from a fixed monitoring station, and OHCA using a time-stratified case-crossover design.
  
  
  
  We observed a V-shaped relationship between preceding mean 24-h and 1-h ambient temperature and the occurrence of OHCAs. For mean 24-h temperature we observed an odds ratio (OR) of 1.05 (1.00-1.11) for each 5°C below the optimum temperature and 1.05 (0.96-1.18) for each 5°C above the optimum. We observed similar results for 1-h mean temperature exposure. Results for temperatures above the optimum temperature showed evidence of confounding by ozone.
  
  
  
  Ambient temperature below an optimum temperature was associated with increased risk of OHCA in Stockholm. Temperature above an optimum temperature was not significantly associated with OHCA.
authors.affiliation: Department of Occupational and Environmental Medicine, Stockholm County Council, Stockholm, Sweden; Unit of Environmental Epidemiology, Institute of Environmental Medicine, Karolinska Institute, Stockholm, Sweden. Electronic address: marcus.dahlquist@ki.se.
authors.forename: Marcus
authors.initials: M
authors.lastname: Dahlquist
authors.affiliation: Department of Occupational and Environmental Medicine, Stockholm County Council, Stockholm, Sweden; Unit of Environmental Epidemiology, Institute of Environmental Medicine, Karolinska Institute, Stockholm, Sweden.
authors.forename: Auriba
authors.initials: A
authors.lastname: Raza
authors.affiliation: Department of Occupational and Environmental Medicine, Stockholm County Council, Stockholm, Sweden; Unit of Environmental Epidemiology, Institute of Environmental Medicine, Karolinska Institute, Stockholm, Sweden.
authors.forename: Getahun
authors.initials: G
authors.lastname: Bero-Bedada
authors.affiliation: Department of Medicine, Solna, Karolinska Institute, Stockholm, Sweden; Department of Cardiology, Stockholm South General Hospital, Stockholm, Sweden.
authors.forename: Jacob
authors.initials: J
authors.lastname: Hollenberg
authors.affiliation: Department of Occupational and Environmental Medicine, Stockholm County Council, Stockholm, Sweden; Unit of Environmental Epidemiology, Institute of Environmental Medicine, Karolinska Institute, Stockholm, Sweden.
authors.forename: Tomas
authors.initials: T
authors.lastname: Lind
authors.affiliation: Unit of Nutritional Epidemiology, Institute of Environmental Medicine, Karolinska Institute, Stockholm, Sweden.
authors.forename: Nicola
authors.initials: N
authors.lastname: Orsini
authors.affiliation: Unit of Work Environmental Toxicology, Institute of Environmental Medicine, Karolinska Institute, Stockholm, Sweden.
authors.forename: Bengt
authors.initials: B
authors.lastname: Sjögren
authors.affiliation: Department of Medicine, Solna, Karolinska Institute, Stockholm, Sweden.
authors.forename: Leif
authors.initials: L
authors.lastname: Svensson
authors.affiliation: Department of Occupational and Environmental Medicine, Stockholm County Council, Stockholm, Sweden; Unit of Environmental Epidemiology, Institute of Environmental Medicine, Karolinska Institute, Stockholm, Sweden; Department of Cardiology, Danderyd Hospital, Stockholm, Sweden.
authors.forename: Petter L
authors.initials: PL
authors.lastname: Ljungman
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000393:Air Pollutants / Q000032:analysis; D000397:Air Pollution / Q000032:analysis; D004784:Environmental Monitoring; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D058687:Out-of-Hospital Cardiac Arrest / Q000453:epidemiology*; D010126:Ozone / Q000032:analysis; D052638:Particulate Matter / Q000032:analysis; D012306:Risk; D013548:Sweden / Q000453:epidemiology; D013696:Temperature
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter; D010126:Ozone
keywords: Ambient temperature; Cardiac arrest; Cardiovascular risk factors; Epidemiology