title: Modest associations between self-reported physical workload and neck trouble: a population-based twin control study.
abstract: OBJECTIVE
  To investigate the relationship between self-reported physical workload and neck trouble (NT) in twins. Additionally, to explore whether the relationship between physical workload and NT is influenced by genetic factors.
  
  
  METHODS
  A twin control study was performed within a population-based, cross-sectional questionnaire study using 3,208 monozygotic (MZ) and same-sexed dizygotic (DZ) twins aged 19-70. Twin pairs discordant for self-reported NT during the past year ("Any NT") were included. Self-reported physical workload in four categories was used as exposure ("sitting," "sitting and walking," "light physical," and "heavy physical" work). Paired analyses including conditional logistic regression were made for all participants and for each sex, and MZ and DZ pairs separately.
  
  
  RESULTS
  No marked associations between physical workload and NT were seen. A moderate risk elevation in "heavy physical" work was seen in DZ men (odds ratio 2.3, 95% confidence intervals 1.3-4.0), but not in MZ men or the MZ or DZ women.
  
  
  CONCLUSIONS
  The findings in some degree supported that "heavy physical" work is a determinant of NT, perhaps only in men, but hardly of any greater importance. The different results between DZ and MZ men suggest that genetic factors influence the relationship between physical workload and NT.
authors.affiliation: Køge Hospital, Køge, Denmark. jcho@regionsjaelland.dk
authors.forename: Jonas Winkel
authors.initials: JW
authors.lastname: Holm
authors.forename: Jan
authors.initials: J
authors.lastname: Hartvigsen
authors.forename: Svend
authors.initials: S
authors.lastname: Lings
authors.forename: Kirsten Ohm
authors.initials: KO
authors.lastname: Kyvik
mesh_terms: D000328:Adult; D000368:Aged; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D019547:Neck Pain / Q000453:epidemiology* / Q000235:genetics; D009784:Occupational Diseases / Q000453:epidemiology* / Q000235:genetics; D015995:Prevalence; D057566:Self Report; D012737:Sex Factors; D014429:Twins, Dizygotic / Q000235:genetics*; D014430:Twins, Monozygotic / Q000235:genetics*; D016526:Workload; D055815:Young Adult