title: Acute coronary syndrome on Friday the 13th: a case for re-organising services?
abstract: BACKGROUND
  Friday the 13th is described as an "unlucky" day that brings misfortune. There are few studies on the question, and none on its effect in cardiovascular patients. The recently misreported "weekend effect" has led to changes in the junior doctor contract in England, providing greater staffing levels on weekends. Should we make similar provisions for Friday the 13th?
  
  
  METHODS
  A retrospective analysis of a large database for patients admitted to hospitals in South Wales with an acute coronary syndrome (ACS) during 1999-2014. Mortality rates for 217 admission day number/name combinations and for Friday the 13th were compared in a Cox proportional hazards regression model.
  
  
  RESULTS
  56 062 ACS patients were identified. There were no significant differences in 13-year mortality between most admission dates (211 of 216) and Friday the 13th. However, a statistically significant reduction in mortality was identified for five dates: Thursday the 15th (HR, 0.77; 95% CI, 0.59-0.999), Wednesday the 18th (HR, 0.76; 95% CI, 0.58-0.99), Monday the 28th (HR, 0.76; 95% CI, 0.57-0.99), Monday the 30th (HR, 0.75; 95% CI, 0.57-0.99) and Tuesday the 31st (HR, 0.71; 95% CI, 0.51-0.99).
  
  
  CONCLUSIONS
  On most days, there was no difference in the 13-year mortality rate for patients admitted with their first ACS from that for "unlucky" Friday the 13th. However, patients admitted on five day/number combinations were 20-30% more likely to survive at 13 years. These findings could be explained by subgroup analysis inflation of the type I error, although supernatural causes merit further investigation. Our findings should be taken into account in future junior doctor contract negotiations, and may provide a case for reduced staffing levels on these lucky days.
authors.affiliation: Cardiff University School of Medicine, Cardiff, Wales, United Kingdom majd@protty.net.
authors.forename: Majd B
authors.initials: MB
authors.lastname: Protty
authors.affiliation: Royal Gwent Hospital, Aneurin Bevan University Health Board, Newport, Wales, United Kingdom.
authors.forename: Mustafa
authors.initials: M
authors.lastname: Jaafar
authors.affiliation: Royal Gwent Hospital, Aneurin Bevan University Health Board, Newport, Wales, United Kingdom.
authors.forename: Sahar
authors.initials: S
authors.lastname: Hannoodee
authors.affiliation: Cardiff University School of Medicine, Cardiff, Wales, United Kingdom.
authors.forename: Phillip
authors.initials: P
authors.lastname: Freeman
mesh_terms: D054058:Acute Coronary Syndrome / Q000401:mortality*; D001363:Awards and Prizes; D006297:Health Services Accessibility / Q000706:statistics & numerical data*; D006301:Health Services Needs and Demand / Q000706:statistics & numerical data; D006801:Humans; D008505:Medical Staff, Hospital / Q000600:supply & distribution; D010343:Patient Admission / Q000706:statistics & numerical data*; D013222:State Medicine / Q000706:statistics & numerical data; D013483:Superstitions; D015996:Survival Rate; D014852:Wales