title: The influence of factors identified in adolescence and early adulthood on social class inequities of musculoskeletal disorders at age 30: a prospective population-based cohort study.
abstract: BACKGROUND
  Social class inequities have been observed for most measures of health. A greater understanding of the relative importance of different explanations is required. In this prospective population-based cohort study we explored the contribution of factors, ascertained at different stages between adolescence and early adulthood, to social class inequities in musculoskeletal disorders (MSD) at age 30.
  
  
  METHODS
  We used data from 547 men and 497 women from a town in north Sweden who were baseline examined at age 16 and followed up to age 30. Using logistic regression models, we estimated the unadjusted odds ratios (OR) for MSD for blue-collar versus white-collar workers in men and women separately. We assessed the contribution of different factors identified between adolescence and early adulthood by comparing the unadjusted OR for social class differences with OR adjusted for these explanatory factors.
  
  
  RESULTS
  We found significant class differences at age 30 with higher MSD among blue-collar workers (OR = 2.03 in men [95% CI: 1.42, 2.90] and 1.98 in women [95% CI: 1.29, 3.02]). After adjustment for explanatory factors, class differences decreased and were no longer significant, with OR of 1.20 in men (95% CI: 0.76, 1.95) and 1.18 in women (95% CI: 0.69, 2.03). School grades at age 16; being single and alcohol consumption at age 21; having children, restricted financial resources, physical activity, alcohol consumption, smoking, and working conditions at age 30 were important for men; parents' social class, school grade, smoking and physical activity at age 16; being single at age 21; and working conditions at age 30 were important for women.
  
  
  CONCLUSIONS
  The accumulation of adverse behavioural and social circumstances from adolescence to early adulthood may be an explanation for the class differences in MSD at age 30. Interventions aimed at reducing health inequities need to consider exploratory factors identified at early and later stages in life, also including structural determinants of health.
authors.affiliation: Occupational Medicine, Department of Public Health and Clinical Medicine, Umeå University, SE-901 85 UMEA, Sweden. masuma.khaatun@fammed.umu.se
authors.forename: Masuma
authors.initials: M
authors.lastname: Khatun
authors.forename: Christina
authors.initials: C
authors.lastname: Ahlgren
authors.forename: Anne
authors.initials: A
authors.lastname: Hammarström
mesh_terms: D000293:Adolescent; D000328:Adult; D000428:Alcohol Drinking; D004522:Educational Status; D005260:Female; D006801:Humans; D008019:Life Style; D017116:Low Back Pain / Q000209:etiology; D008297:Male; D009140:Musculoskeletal Diseases / Q000209:etiology*; D019547:Neck Pain / Q000209:etiology; D011446:Prospective Studies; D012737:Sex Factors; D012847:Single Person; D012923:Social Class; D012931:Social Environment