title: Excess cardiac mortality on Monday: the importance of gender, age and hospitalisation.
abstract: BACKGROUND
  Available evidence suggests a peak in the incidence of cardiovascular events on Mondays compared to other days of the week. The underlying mechanism may be summarised as naturally occurring rhythmic fluctuations in human physiology, and socially determined rhythms in human behaviour. Change in these rhythms may lead to attenuation of the peak on Mondays.
  
  
  OBJECTIVE
  To quantify the excess risk associated with the Monday peak in cardiovascular mortality and to explore the role of age, gender and hospitalisation.
  
  
  METHODS
  Details on time and cause of all deaths which occurred in the city of Rotterdam between November 21, 1988 and November 21, 1990 were obtained by sending a questionnaire to the physician who signed the death certificate. We studied the weekly distribution of 1828 confirmed cases of sudden cardiac death, for the group as a whole and in subgroups according to gender, age (< 65 years/65 years) and hospitalisation.
  
  
  RESULTS
  The odds ratio (OR) of sudden cardiac death on Monday compared to other days of the week was 1.20 (95% CI: 1.06-1.36). The excess mortality due to the Monday peak amounted to 4.9 per 1000 deaths. The Monday peak was more pronounced in non-hospitalised (OR: 1.25; 95% CI: 1.08-1.44) than in hospitalised patients (OR: 1.06; 95% CI: 0.83-1.37), in men (OR: 1.25; 95% CI: 1.06-1.48) than in women (OR: 1.14; 95% CI: 0.95-1.36), and in those younger than 65 (OR: 1.29; 95% CI: 0.95-1.74) compared to those aged 65 years or over (OR: 1.18; 95% CI: 1.03-1.35). Yet, the confidence limits overlap.
  
  
  CONCLUSIONS
  The incidence of sudden cardiac death is markedly increased on Monday, more pronounced in non-hospitalised patients. Our results may point to the relevance of naturally occurring rhythmic fluctuations in human physiology, and socially determined rhythms in human behaviour as underlying mechanism.
authors.affiliation: Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: D R
authors.initials: DR
authors.lastname: Witte
authors.forename: D E
authors.initials: DE
authors.lastname: Grobbee
authors.forename: M L
authors.initials: ML
authors.lastname: Bots
authors.forename: A W
authors.initials: AW
authors.lastname: Hoes
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D050197:Atherosclerosis; D002940:Circadian Rhythm; D016757:Death, Sudden, Cardiac / Q000453:epidemiology*; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D012737:Sex Factors; D012919:Social Behavior; D011795:Surveys and Questionnaires; D013997:Time Factors