title: [Seasonal variations in admissions for acute myocardial infarction. The PRIMVAC study].
abstract: OBJECTIVE
  Some authors have described seasonal variations in the incidence of acute myocardial infarction. The aim of this study was to determine the existence of seasonal rhythms in admissions for acute myocardial infarction to coronary care units, and in mortality, and to analyze the influence of age on environmental factors.
  
  
  METHODS
  The study included a total of 8400 consecutive patients with acute myocardial infarction admitted to 12 coronary care units in the PRIMVAC registry from January 1995 to December 1999. Seasonal rhythms were analyzed with the time series method and the Cosinor regression equation. The influence of age was analyzed with the chi 2 test.
  
  
  RESULTS
  The total number of admissions increased in winter and decreased in summer. The highest peak (acrophase) occurred in winter, with 2183 cases (r2=0.91), specifically in February, with 742 cases (r2=0.66). The age of the patients conditioned seasonal variations (P=.006), and the influence was statistically significant for patients over 65 years of age. Changes in mortality with time did not reach statistical significance.
  
  
  CONCLUSIONS
  A seasonal rhythm in admissions for acute myocardial infarction was found, with an increase in winter and a decrease in summer. Age conditioned the effect of environmental factors on acute myocardial infarction, and patients aged 65 years or older were more sensitive to mechanisms that led to increases in admissions in winter.
authors.affiliation: Unidad de Cuidados Intensivos. Hospital La Plana. Villareal. Castellón. España. gonzalez_enr@gva.es
authors.forename: Enrique
authors.initials: E
authors.lastname: González Hernández
authors.forename: Adolfo
authors.initials: A
authors.lastname: Cabadés O'Callaghan
authors.forename: Javier
authors.initials: J
authors.lastname: Cebrián Doménech
authors.forename: Vicente
authors.initials: V
authors.lastname: López Merino
authors.forename: Rafael
authors.initials: R
authors.lastname: Sanjuán Mañez
authors.forename: Ildefonso
authors.initials: I
authors.lastname: Echánove Errazti
authors.forename: José
authors.initials: J
authors.lastname: Valencia Martín
authors.forename: Vicente
authors.initials: V
authors.lastname: Bertomeu Martínez
mesh_terms: D017677:Age Distribution; D000368:Aged; D003080:Cold Temperature; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D009203:Myocardial Infarction / Q000453:epidemiology*; D012042:Registries; D012044:Regression Analysis; D012621:Seasons; D013030:Spain / Q000453:epidemiology