title: Exploring the periodicity of cardiovascular events in Switzerland: variation in deaths and hospitalizations across seasons, day of the week and hour of the day.
abstract: OBJECTIVE
  The purpose of this study is to explore the periodical patterns of events and deaths related to cardiovascular disease (CVD), acute myocardial infarction (AMI) and stroke in Swiss adults (≥ 18 years).
  
  
  METHODS
  Mortality data for period 1969-2007 (N=869,863 CVD events) and hospitalization data for period 1997-2008 (N=959,990 CVD events) were used. The annual, weekly and circadian distribution of CVD-related deaths and events were assessed. Multivariate analysis was conducted using multinomial logistic regression adjusting for age, gender and calendar year and considering deaths from respiratory diseases, accidents or other causes as competitive events.
  
  
  RESULTS
  CVD deaths and hospitalizations occurred less frequently in the summer months. Similar patterns were found for AMI and stroke. No significant weekly variation for CVD deaths was found. Stratification by age and gender showed subjects aged <65 years to present a higher probability of dying on Mondays and Saturday, only for men. This finding was confirmed after multivariate adjustment. Finally, a circadian variation in CVD mortality was observed, with a first peak in the morning (8-12 am) and a smaller second peak in the late afternoon (2-6 pm). This pattern persisted after multivariate adjustment and was more pronounced for AMI than for stroke.
  
  
  CONCLUSIONS
  There is a periodicity of hospitalizations and deaths related to CVD, AMI and stroke in Switzerland. This pattern changes slightly according to the age and sex of the subjects. Although the underlying mechanisms are not fully identified, preventive measures should take into account these aspects to develop better strategies of prevention and management of CVD.
authors: Institute of Social and Preventive Medicine (IUMSP), Lausanne University Hospital, Switzerland. Electronic address: Michelle.Reavey@unil.ch.
authors: Michelle
authors: M
authors: Reavey
authors: Hugo
authors: H
authors: Saner
authors: Fred
authors: F
authors: Paccaud
authors: Pedro
authors: P
authors: Marques-Vidal
mesh_terms: D000368:Aged; D002318:Cardiovascular Diseases / Q000401:mortality* / Q000503:physiopathology / Q000628:therapy; D002940:Circadian Rhythm; D005260:Female; D005500:Follow-Up Studies; D017052:Hospital Mortality / Q000639:trends; D006760:Hospitalization / Q000639:trends*; D006801:Humans; D008297:Male; D012189:Retrospective Studies; D012621:Seasons; D015996:Survival Rate / Q000639:trends; D013557:Switzerland / Q000453:epidemiology
keywords: AMI; CVD; Daily; Hourly variation; Seasonality; Stroke