title: Diurnal variations in incidence and outcome of out-of-hospital cardiac arrest including prior comorbidity and pharmacotherapy: a nationwide study in Denmark.
abstract: OBJECTIVE
  To investigate diurnal variations in incidence and outcomes following out-of-hospital cardiac arrest (OHCA).
  
  
  METHODS
  OHCA of presumed cardiac etiology were identified through the nationwide Danish Cardiac Arrest Registry (2001-2010). Time of day was divided into three time periods: daytime 07.00-14.59; evening 15.00-22.59; and nighttime 23.00-06.59.
  
  
  RESULTS
  We identified 18,929 OHCA patients, aged ≥18 years. The median age was 72 years (IQR 62-80) and the majority were male (67.5%). OHCA occurrence varied across time periods, with 43.9%, 35.7% and 20.6% occurring during daytime, evening and nighttime, respectively. Nighttime patients were more likely to have: severe comorbidity (i.e. COPD), arrest in private home (87.2% vs. 69.0% and 73.0% daytime and evening, respectively), non-witnessed arrest (51.2% vs. 48.4% and 43.7%), no bystander CPR (75.9% vs. 68.4% and 66.1%), longer time interval from recognition of OHCA to rhythm analysis (12 min vs. 11 min and 11 min), and non-shockable heart rhythm (80.1% vs. 70.3% and 69.4%), all p<0.0001. Nighttime patients were less likely to achieve return of spontaneous circulation on arrival at the hospital (7.5% vs. 14.8% and 15.1%) and 1-year survival (2.8% vs. 7.2% and 7.1%), p<0.0001. Overall, the lower 1-year survival rate persisted after adjusting for patient-related and cardiac-arrest related characteristics mentioned above (OR 0.47, 95%CI 0.37-0.59; OR 0.51, 95%CI 0.40-0.65, compared to daytime and evening, respectively).
  
  
  CONCLUSIONS
  We found nighttime patients to have a lower survival compared to daytime and evening that persisted when adjusting for patient-related and cardiac-arrest related characteristics including comorbidities.
authors: Department of Cardiology, Copenhagen University Hospital Gentofte, Niels Andersens Vej 65, 2900 Hellerup, Denmark. Electronic address: limkarlsson@gmail.com.
authors: Lena I M
authors: LI
authors: Karlsson
authors: Department of Cardiology, Copenhagen University Hospital Gentofte, Niels Andersens Vej 65, 2900 Hellerup, Denmark.
authors: Mads
authors: M
authors: Wissenberg
authors: The Heart Centre, Copenhagen University Hospital Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark.
authors: Emil L
authors: EL
authors: Fosbøl
authors: Department of Cardiology, Copenhagen University Hospital Gentofte, Niels Andersens Vej 65, 2900 Hellerup, Denmark.
authors: Carolina Malta
authors: CM
authors: Hansen
authors: Emergency Medicine and EMS, Head Office, Capital Region of Denmark, Blegdamsvej 9, 2100 Copenhagen, Denmark.
authors: Freddy K
authors: FK
authors: Lippert
authors: St. Michael's Hospital, University of Toronto, 30 Bond Street, Toronto, Ontario M5B 1W8, Canada.
authors: Akshay
authors: A
authors: Bagai
authors: Emory University School of Medicine, Rollins School of Public Health, 1648 Pierce Drive Northeast, Atlanta, GA 30307, USA.
authors: Bryan
authors: B
authors: McNally
authors: Duke Clinical Research Institute, 2400 Pratt Street, Durham, NC, USA.
authors: Christopher B
authors: CB
authors: Granger
authors: Prehospital Medical Emergency Services, Central Denmark Region, Olof Palmes Allé 34, 8200 Aarhus N, Denmark.
authors: Erika Frischknecht
authors: EF
authors: Christensen
authors: Department of Cardiology, Copenhagen University Hospital Gentofte, Niels Andersens Vej 65, 2900 Hellerup, Denmark.
authors: Fredrik
authors: F
authors: Folke
authors: Department of Cardiology, Copenhagen University Hospital Gentofte, Niels Andersens Vej 65, 2900 Hellerup, Denmark.
authors: Shahzleen
authors: S
authors: Rajan
authors: Department of Cardiology, Copenhagen University Hospital Gentofte, Niels Andersens Vej 65, 2900 Hellerup, Denmark.
authors: Peter
authors: P
authors: Weeke
authors: Emergency Medicine and EMS, Head Office, Capital Region of Denmark, Blegdamsvej 9, 2100 Copenhagen, Denmark.
authors: Søren L
authors: SL
authors: Nielsen
authors: The Heart Centre, Copenhagen University Hospital Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark.
authors: Lars
authors: L
authors: Køber
authors: Department of Cardiology, Copenhagen University Hospital Gentofte, Niels Andersens Vej 65, 2900 Hellerup, Denmark; National Institute of Public Health, University of Southern Denmark, Øster Farimagsgade 5A, 1353 Copenhagen K, Denmark.
authors: Gunnar H
authors: GH
authors: Gislason
authors: The Institute of Health, Science and Technology, Niels Jernes Vej 12, 9220 Aalborg, Denmark.
authors: Christian
authors: C
authors: Torp-Pedersen
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002940:Circadian Rhythm; D003718:Denmark; D004358:Drug Therapy; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D058687:Out-of-Hospital Cardiac Arrest / Q000150:complications / Q000453:epidemiology*; D013997:Time Factors
keywords: Cardiac arrest; Diurnal variation; Resuscitation; Survival