title: Joint effect of self-reported sleep problems and three components of the metabolic syndrome on risk of coronary heart disease.
abstract: OBJECTIVE
  This study explored the joint effect of two epidemics, sleep problems and metabolic syndrome (MetS), on the risk of coronary heart disease (CHD).
  
  
  METHODS
  The study group is part of the Finnish middle-aged men who participated in the first screening for the Helsinki Heart Study (HHS) in 1981-1982. At that time, three components of MetS were measured: body mass index, HDL cholesterol, and blood pressure. Later, in 1986-1988, they were given a psychosocial questionnaire including items on sleep problems. Of the respondents, 2753 formed our study group and were followed up using population-based registers until 1995. The relative risks (RR) of CHD were estimated using Cox's regression models.
  
  
  RESULTS
  When several sleep problems were present simultaneously, some increased CHD risk was observed. However, when considered jointly with MetS, insomnia or daytime fatigue approximately doubled the CHD risk and the presence of insufficient sleep more than tripled the risk. Among those who had MetS only, the RR was 2.55, and among those with both insufficient sleep and MetS the RR was 9.36 (95% confidence interval: 4.60-19.04; P for interaction 0.09) when compared to those with no insufficient sleep and no components of MetS.
  
  
  CONCLUSIONS
  The interaction occurred when all three measured MetS components were present, suggesting that co-occurrence of these two epidemics may predict growing public health problems.
authors.affiliation: University of Tampere, Tampere School of Public Health, Tampere, Finland; Helsinki Heart Study, Helsinki, Finland. minna.loponen@uta.fi
authors.forename: Minna
authors.initials: M
authors.lastname: Loponen
authors.forename: Christer
authors.initials: C
authors.lastname: Hublin
authors.forename: Raija
authors.initials: R
authors.lastname: Kalimo
authors.forename: Matti
authors.initials: M
authors.lastname: Mänttäri
authors.forename: Leena
authors.initials: L
authors.lastname: Tenkanen
mesh_terms: D003327:Coronary Disease / Q000453:epidemiology / Q000209:etiology*; D005387:Finland; D006801:Humans; D008297:Male; D024821:Metabolic Syndrome / Q000150:complications* / Q000453:epidemiology; D012042:Registries; D012306:Risk; D018570:Risk Assessment; D012307:Risk Factors; D012720:Severity of Illness Index; D012893:Sleep Wake Disorders / Q000150:complications* / Q000453:epidemiology; D011795:Surveys and Questionnaires