title: Smoking and low back pain: is the association real?
abstract: METHODS
  A review was made of the epidemiological literature on the association between smoking and low back pain (LBP).
  
  
  OBJECTIVE
  The first objectives was to identify studies that challenged their preliminary results with additional test factors and to see what effect this had on the outcomes. The second objective was to identify test factors that were unique to studies in which the original association disappeared after multivariate analysis.
  
  
  BACKGROUND
  The literature on this subject is confusing and no systemic investigation seems to have been made on the possibility of spurious data interpretation.
  
  
  METHODS
  Twenty-four articles reporting on 126 epidemiological studies (in 24 reports) on the association between smoking and LBP were systematically reviewed by the authors, independently and jointly.
  
  
  RESULTS
  In eight of the thirteen studies that tested a preliminary positive association between smoking and LBP, this association remained after multivariate analysis, whereas it disappeared in after analysis in five. Two variables, marital status and occupation, were uniquely present in some of the studies in which the initial positive association was lost. However, their study samples were probably nonrepresentative of the general population.
  
  
  CONCLUSIONS
  A more strategic approach is needed in the study of the role of extraneous factors. In particular, marital status and occupation should be further investigated.
authors.affiliation: Nordic Institute for Chiropractic and Clinical Biomechanics, Odense, Denmark.
authors.forename: C
authors.initials: C
authors.lastname: Leboeuf-Yde
authors.forename: A
authors.initials: A
authors.lastname: Yashin
mesh_terms: D004812:Epidemiologic Methods; D006801:Humans; D015994:Incidence; D017116:Low Back Pain / Q000453:epidemiology / Q000209:etiology*; D015999:Multivariate Analysis; D012680:Sensitivity and Specificity; D012907:Smoking / Q000009:adverse effects* / Q000453:epidemiology