title: Association of lifestyle-related factors with circadian onset patterns of acute myocardial infarction: a prospective observational study in Japan.
abstract: OBJECTIVE
  The onset of acute myocardial infarction (AMI) shows characteristic circadian variations involving a definite morning peak and a less-defined night-time peak. However, the factors influencing the circadian patterns of AMI onset and their influence on morning and night-time peaks have not been fully elucidated.
  
  
  METHODS
  An analysis of patients registered between 1998 and 2008 in the Osaka Acute Coronary Insufficiency Study, which is a prospective, multicentre observational study of patients with AMI in the Osaka region of Japan. The present study included 7755 consecutive patients with a known time of AMI onset.
  
  
  METHODS
  A mixture of two von Mises distributions was used to examine whether a circadian pattern of AMI had uniform, unimodal or bimodal distribution, and the likelihood ratio test was then used to select the best circadian pattern among them. The hierarchical likelihood ratio test was used to identify factors affecting the circadian patterns of AMI onset. The Kaplan-Meier method was used to estimate survival curves of 1-year mortality according to AMI onset time.
  
  
  RESULTS
  The overall population had a bimodal circadian pattern of AMI onset characterised by a high and sharp morning peak and a lower and less-defined night-time peak (bimodal p<0.001). Although several lifestyle-related factors had a statistically significant association with the circadian patterns of AMI onset, serum triglyceride levels had the most prominent association with the circadian patterns of AMI onset. Patients with triglyceride ≥150 mg/dL on admission had only one morning peak in the circadian pattern of AMI onset during weekdays, with no peaks detected on weekends, whereas all other subgroups had two peaks throughout the week.
  
  
  CONCLUSIONS
  The circadian pattern of AMI onset was characterised by bimodality. Notably, several lifestyle-related factors, particularly serum triglyceride levels, had a strong relation with the circadian pattern of AMI onset.
  
  
  BACKGROUND
  UMIN000004575.
authors.affiliation: Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Japan Department of Biomedical Statistics, Osaka University Graduate School of Medicine, Suita, Japan.
authors.forename: Ryuya
authors.initials: R
authors.lastname: Edahiro
authors.affiliation: Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Japan Department of Advanced Cardiovascular Therapeutics, Osaka University Graduate School of Medicine, Suita, Japan Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan.
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Sakata
authors.affiliation: Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Japan.
authors.forename: Daisaku
authors.initials: D
authors.lastname: Nakatani
authors.affiliation: Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Japan.
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Suna
authors.affiliation: Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Japan.
authors.forename: Masaya
authors.initials: M
authors.lastname: Usami
authors.affiliation: Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Japan.
authors.forename: Sen
authors.initials: S
authors.lastname: Matsumoto
authors.affiliation: Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Japan.
authors.forename: Masahiko
authors.initials: M
authors.lastname: Hara
authors.affiliation: Department of Social and Environmental Medicine, Osaka University Graduate School of Medicine, Suita, Japan.
authors.forename: Tetsuhisa
authors.initials: T
authors.lastname: Kitamura
authors.affiliation: School of Human Welfare Studies Health Care Center and Clinic, Kwansei Gakuin University, Nishinomiya, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Sato
authors.affiliation: Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Japan Department of Community Medicine, Osaka University Graduate School of Medicine, Suita, Japan.
authors.forename: Shizuya
authors.initials: S
authors.lastname: Yamashita
authors.affiliation: Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Japan Department of Advanced Cardiovascular Therapeutics, Osaka University Graduate School of Medicine, Suita, Japan.
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Nanto
authors.affiliation: Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Japan.
authors.forename: Shungo
authors.initials: S
authors.lastname: Hikoso
authors.affiliation: Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Sakata
authors.affiliation: Osaka Prefectural Hospital Organization, Osaka Medical Center for Cancer and Cardiovascular Diseases, Osaka, Japan.
authors.forename: Masatsugu
authors.initials: M
authors.lastname: Hori
authors.affiliation: Department of Biomedical Statistics, Osaka University Graduate School of Medicine, Suita, Japan.
authors.forename: Toshimitsu
authors.initials: T
authors.lastname: Hamasaki
authors.affiliation: Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Japan Department of Cardiovascular Medicine, University of Tokyo Graduate School of Medicine, Tokyo, Japan.
authors.forename: Issei
authors.initials: I
authors.lastname: Komuro
mesh_terms: D000368:Aged; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008019:Life Style; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000453:epidemiology*; D011446:Prospective Studies