title: A 12 year prospective study of circulatory disease among Danish shift workers.
abstract: BACKGROUND
  Previous studies of the risk of heart disease after shift work reached different estimates and review authors disagree about the validity of some of the studies. A cross sectional study showed that shift workers had a higher prevalence of nearly every unfavourable work environment factor investigated. Conflicts at work and low decision latitude were more frequent among shift workers, and all-day walking or standing work and part-time jobs were more often found among female shift workers.
  
  
  OBJECTIVE
  To estimate the risk of circulatory disease in a prospective follow up of a representative sample of gainfully employed Danes, considering known or suspected confounding factors.
  
  
  METHODS
  A cohort of 5517 people who were gainfully employed in 1990 were followed up for all hospital treatments due to circulatory diseases (390-458, ICD-8; I00-I99, ICD-10) from 1991 to 2002 inclusive. A log linear Poisson regression model was applied to control confounding factors and calculate the relative risk for 927 men and women working nights, evenings, or other non-day shifts compared to 4579 day workers.
  
  
  RESULTS
  Non-day workers compared to day workers had a relative risk (RR) for all circulatory diseases of 1.31 (95% CI 1.06-1.63). Without control for BMI and smoking, the RR estimate was 1.33 (95% CI 1.07-1.65). For a subgroup of workers with at least three years' seniority, the RR was 1.40 (95% CI 1.09-1.81). The population based aetiological fraction of shift work was estimated to 5%.
  
  
  CONCLUSIONS
  This study adds to a growing body of evidence suggesting that shift work carries an excess risk of circulatory diseases.
authors.affiliation: National Institute of Occupational Health, Copenhagen, Denmark. ft@ami.dk
authors.forename: F
authors.initials: F
authors.lastname: Tüchsen
authors.forename: H
authors.initials: H
authors.lastname: Hannerz
authors.forename: H
authors.initials: H
authors.lastname: Burr
mesh_terms: D000328:Adult; D015992:Body Mass Index; D002318:Cardiovascular Diseases / Q000453:epidemiology*; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000453:epidemiology; D009784:Occupational Diseases / Q000453:epidemiology*; D011446:Prospective Studies; D012042:Registries; D012307:Risk Factors; D017678:Sex Distribution; D012907:Smoking / Q000453:epidemiology; D014940:Work Schedule Tolerance / Q000502:physiology*