title: Seasonal variation in hospital admission in patients with heart failure and its effect on prognosis.
abstract: BACKGROUND
  A seasonal variation in hospital admissions in patients with heart failure (HF) has been described and most admissions occur during the winter season. The effect of this seasonal variation on prognosis is less clear.
  
  
  OBJECTIVE
  To evaluate the effect of the seasonal timing of hospital admission on clinical outcome in patients with HF.
  
  
  METHODS
  We prospectively enrolled 362 consecutive patients hospitalized with a definite clinical diagnosis of HF during a 2-year period. Patients were followed clinically for a period of 1 year.
  
  
  RESULTS
  There was a prominent seasonal variation in hospital admissions in patients with HF with peak admissions during the winter. The admission rate inversely correlated with the average monthly temperature. Admission during the summer season was a significant predictor of reduced survival (59 vs. 75%, p < 0.01). Cox regression analysis demonstrated that independent predictors of reduced survival after adjustment for other predictors were admission during the hottest 6 months or admission during the summer. In addition, increased mean environmental admission temperature was an independent predictor of reduced survival.
  
  
  CONCLUSIONS
  Seasonal temperature has a significant effect on the rate of hospital admission in patients with HF. Admission during warmer weather is a sign of a poor prognosis.
authors.affiliation: Heart Institute, Hadassah University Hospital, Jerusalem, Israel. igotsman@bezeqint.net
authors.forename: Israel
authors.initials: I
authors.lastname: Gotsman
authors.forename: Donna
authors.initials: D
authors.lastname: Zwas
authors.forename: Dan
authors.initials: D
authors.lastname: Admon
authors.forename: Chaim
authors.initials: C
authors.lastname: Lotan
authors.forename: Andre
authors.initials: A
authors.lastname: Keren
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006333:Heart Failure / Q000401:mortality*; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D012621:Seasons