title: Interactions between physical and psychosocial demands of work associated to low back pain.
abstract: OBJECTIVE
  To examine the interaction between physical and psychosocial demands of work associated to low back pain.
  
  
  METHODS
  Cross-sectional study carried out in a stratified proportional random sample of 577 plastic industry workers in the metropolitan area of the city of Salvador, Northeast Brazil in 2002. An anonymous standard questionnaire was administered in the workplace by trained interviewers. Physical demands at work were self-rated on a 6-point numeric scale, with anchors at each end of the scale. Factor analysis was carried out on 11 physical demand variables to identify underlying factors. Psychosocial work demands were measured by demand, control and social support questions. Multivariate analysis was performed using the likelihood ratio test.
  
  
  RESULTS
  The factor analysis identified two physical work demand factors: material handling (factor 1) and repetitiveness (factor 2). The multiple logistic regression analysis showed that factor 1 was positively associated with low back pain (OR=2.35, 95% CI 1.50;3.66). No interaction was found between physical and psychosocial work demands but both were independently associated to low back pain.
  
  
  CONCLUSIONS
  The study found independent effects of physical and psychosocial work demands on low back pain prevalence and emphasizes the importance of physical demands especially of material handling involving trunk bending forward and trunk rotation regardless of age, gender, and body fitness.
authors.affiliation: Departamento de Medicina Preventiva e Social, Faculdade de Medicina da Bahia, Universidade Federal da Bahia, Salvador, BA, Brazil. ritafernandes@ufba.br
authors.forename: Rita de Cássia Pereira
authors.initials: Rde C
authors.lastname: Fernandes
authors.forename: Fernando Martins
authors.initials: FM
authors.lastname: Carvalho
authors.forename: Ada Avila
authors.initials: AA
authors.lastname: Assunção
authors.forename: Annibal Muniz
authors.initials: AM
authors.lastname: Silvany Neto
mesh_terms: D000328:Adult; D001938:Brazil / Q000453:epidemiology; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007588:Job Satisfaction; D017116:Low Back Pain / Q000453:epidemiology / Q000209:etiology* / Q000523:psychology*; D008297:Male; D009784:Occupational Diseases / Q000453:epidemiology / Q000209:etiology* / Q000523:psychology; D012307:Risk Factors; D011795:Surveys and Questionnaires