title: Is there a clinically significant seasonal component to hospital admissions for atrial fibrillation?
abstract: BACKGROUND
  Atrial fibrillation is a common cardiac dysrhythmia, particularly in the elderly. Recent studies have indicated a statistically significant seasonal component to atrial fibrillation hospitalizations.
  
  
  METHODS
  We conducted a retrospective population cohort study using time series analysis to evaluate seasonal patterns of atrial fibrillation hospitalizations for the province of Ontario for the years 1988 to 2001. Five different series methods were used to analyze the data, including spectral analysis, X11, R-Squared, autocorrelation function and monthly aggregation.
  
  
  RESULTS
  This study found evidence of weak seasonality, most apparent at aggregate levels including both ages and sexes. There was dramatic increase in hospitalizations for atrial fibrillation over the years studied and an age dependent increase in rates per 100,000. Overall, the magnitude of seasonal difference between peak and trough months is in the order of 1.4 admissions per 100,000 population. The peaks for hospitalizations were predominantly in April, and the troughs in August.
  
  
  CONCLUSIONS
  Our study confirms statistical evidence of seasonality for atrial fibrillation hospitalizations. This effect is small in absolute terms and likely not significant for policy or etiological research purposes.
authors.affiliation: Primary Care Research Unit, Sunnybrook and Women's College Health Sciences Centre, 2075 Bayview Avenue, #E-349, Toronto, Ontario, Canada M4N 3M5. rupshur@idirect.com
authors.forename: Ross E G
authors.initials: RE
authors.lastname: Upshur
authors.forename: Rahim
authors.initials: R
authors.lastname: Moineddin
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Crighton
authors.forename: Muhammad
authors.initials: M
authors.lastname: Mamdani
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D001281:Atrial Fibrillation / Q000453:epidemiology* / Q000628:therapy; D002909:Chronobiology Phenomena; D005260:Female; D006761:Hospitals / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009864:Ontario / Q000453:epidemiology; D010343:Patient Admission / Q000706:statistics & numerical data* / Q000639:trends; D012189:Retrospective Studies; D012621:Seasons; D017678:Sex Distribution; D014600:Utilization Review