title: Seasonal variations in out of hospital cardiopulmonary arrest.
abstract: OBJECTIVE
  To determine whether there are seasonal variations in survival following out of hospital cardiopulmonary arrest.
  
  
  METHODS
  Prospective cohort study using the Heartstart (Scotland) database.
  
  
  METHODS
  All of Scotland.
  
  
  METHODS
  10 890 people who suffered out of hospital cardiopulmonary arrest in the summer or winter between December 1988 and August 1997 inclusive.
  
  
  METHODS
  Univariate comparisons of 5406 arrests occurring in summer with 5484 in winter, in terms of patient characteristics, management, and survival using chi(2) and Mann-Whitney U tests. Multivariate analysis of the association between season and survival following adjustment for case mix.
  
  
  METHODS
  Survival to discharge from hospital, survival pre-admission, in-hospital survival.
  
  
  RESULTS
  Only 6% of people who arrested in winter survived to discharge, compared to 8% of those who arrested in summer (odds ratio 0.77, p < 0.001). People who arrested in winter had a poorer risk profile in that they were older, more likely to arrest at home, less likely to have a witness, and less likely to receive defibrillation. However, after adjustment for case mix, people who arrested in winter were still 19% less likely to survive compared to those who arrested in summer. Deaths pre-admission were significantly higher in winter (odds ratio 1.18, p < 0.05) but in-hospital deaths were not.
  
  
  CONCLUSIONS
  People who suffer cardiopulmonary arrest in winter have a significantly lower likelihood of surviving. This is, in part, caused by the higher frequency of a number of recognised risk factors. However, their prognosis remains poorer even after adjustment for these factors.
authors.affiliation: Department of Public Health Medicine, Greater Glasgow Health Board, Dalian House, 350 St Vincents Street, Glasgow G3 8YU, UK. jill.pell@glasgow-hb.scot.nhs.uk
authors.forename: J P
authors.initials: JP
authors.lastname: Pell
authors.forename: J
authors.initials: J
authors.lastname: Sirel
authors.forename: A K
authors.initials: AK
authors.lastname: Marsden
authors.forename: S M
authors.initials: SM
authors.lastname: Cobbe
mesh_terms: D000368:Aged; D005260:Female; D006323:Heart Arrest / Q000209:etiology / Q000401:mortality* / Q000628:therapy; D006801:Humans; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D011379:Prognosis; D012606:Scotland / Q000453:epidemiology; D012621:Seasons; D015996:Survival Rate