title: Historical cohort study of shift work and blood pressure.
abstract: BACKGROUND
  It has been suggested that shift work (SW) is associated with changes in blood pressure (BP). However, studies have reported contradictory results.
  
  
  OBJECTIVE
  To prospectively examine the association between SW and BP among male workers.
  
  
  METHODS
  A historical cohort study, involving workers of Esfahan's Mobarakeh Steel Company, in Iran, was conducted over 14 years. The association between SW, systolic BP (SBP) and diastolic BP (DBP) was investigated after adjusting for body mass index, age, work experience, marriage, smoking and education based on the Bayesian multilevel modelling approach.
  
  
  RESULTS
  The study sample included 5331 male workers. The mean age (standard deviation, SD) was 34.8 (6.6) years and mean work (SD) experience was 9.4 (6.1) years. Among these subjects, 2348 (44%), 340 (6%) and 2643 (50%) were day workers, weekly rotating shift workers and routinely rotating shift workers, respectively. The mean SBP (SD) and DBP (SD) of these workers were 118.7 (8.1) and 73.1 (6.7) mmHg, respectively. After controlling for several confounding variables, there was no significant relationship between SBP and DBP and SW.
  
  
  CONCLUSIONS
  No significant association between SW and BP was observed among these three groups (day workers, weekly rotating shift workers and routinely rotating shift workers). Prospective studies, which control for confounding factors, such as the healthy worker effect, occupational history, family history and psychological factors (e.g. occupational stress and job satisfaction), are required to evaluate this further.
authors: Biostatistics Department, Faculty of Medical Sciences, Tarbiat Modares University, Tehran 1411713116, Iran.
authors: M
authors: M
authors: Gholami Fesharaki
authors: A
authors: A
authors: Kazemnejad
authors: F
authors: F
authors: Zayeri
authors: M
authors: M
authors: Rowzati
authors: H
authors: H
authors: Akbari
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D015331:Cohort Studies; D006801:Humans; D007492:Iran; D008297:Male; D009787:Occupational Medicine; D011446:Prospective Studies; D014940:Work Schedule Tolerance / Q000502:physiology*
keywords: Bayesian multilevel modelling; Iran; blood pressure; historical cohort study; shift work.