title: Occupational and other predictors of herniated lumbar disc disease-a 33-year follow-up in the Copenhagen male study.
abstract: METHODS
  Cohort study.
  
  
  OBJECTIVE
  To examine the association between self-reported physical workload and risk of herniated lumbar disc disease (HLDD) in a long-term follow-up of men without a history of back disorders at baseline.
  
  
  BACKGROUND
  Heavy physical workload is considered a risk factor for HLDD, but the issue is not definitively settled.
  
  
  METHODS
  The Copenhagen Male Study is a prospective cohort study established in 1970 to 1971. At baseline, 5245 men answered a questionnaire about history of back disease and physical workload. Psychosocial working conditions, lifestyle, social class, and measured height and weight were included as potential confounders. Information about hospitalization due to HLDD was obtained from the National Hospital Register covering the period from 1977 to 2003. Hazard ratios were calculated by Cox proportional hazard regression model.
  
  
  RESULTS
  Among 3833 men without back disease history at baseline, the strongest predictor of hospitalization for HLDD was frequent strenuous physical activity at work; compared with unexposed, the hazard ratio with 95% confidence interval was 3.90 (1.82-8.38). Also, body height was a significant predictor, whereas body weight was only insignificantly associated with HLDD.
  
  
  CONCLUSIONS
  Among men without history of back disease reporting of frequent exposure to strenuous physical activity at work was a strong risk factor for later hospitalization due to HLDD.
authors.affiliation: Copenhagen Male Study, Epidemiological Research Unit, Clinic of Occupational and Environmental Medicine, Bispebjerg University Hospital, Copenhagen, Denmark.
authors.forename: Inge Gregersen
authors.initials: IG
authors.lastname: Sørensen
authors.forename: Peter
authors.initials: P
authors.lastname: Jacobsen
authors.forename: Finn
authors.initials: F
authors.lastname: Gyntelberg
authors.forename: Poul
authors.initials: P
authors.lastname: Suadicani
mesh_terms: D000328:Adult; D015331:Cohort Studies; D003718:Denmark / Q000453:epidemiology; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D007405:Intervertebral Disc Displacement / Q000150:complications*; D008019:Life Style; D017116:Low Back Pain / Q000453:epidemiology* / Q000209:etiology; D008297:Male; D008875:Middle Aged; D009784:Occupational Diseases / Q000150:complications*; D016016:Proportional Hazards Models; D012042:Registries / Q000706:statistics & numerical data; D012044:Regression Analysis; D012307:Risk Factors; D012923:Social Class; D011795:Surveys and Questionnaires; D016019:Survival Analysis; D016526:Workload; D017132:Workplace