DOES SMOKING CAUSE LOW-BACK-PAIN - A REVIEW OF THE EPIDEMIOLOGIC LITERATURE FOR CAUSALITY

Background: Smoking has been associated with low back pain (LBP) in se veral epidemiologic studies but the results are contradictory. Despite this, smoking is often assumed to be a causative factor of LBP. Study Objective: To appraise the epidemiologic literature to establish whet her there is evidence for a causal link between smoking and LBP. Data Sources: Twenty-two original research reports published between 1974 a nd 1993 were reviewed and a systematic investigation was made of eight of these, which were retained because they included study samples rep resentative of their target populations. Data synthesis: To uncover an y evidence for a causal relationship between smoking and LBP, these ei ght reports were examined in detail for strength of association, dose- response effect, temporality and consistency of findings. Results: Som e studies found a positive association between smoking and LBP; when p resent, the strength of this association was generally small. Some ass ociations remained unchanged after multivariate analysis, whereas othe rs became statistically nonsignificant. Contradictory results were als o noted in studies which reported on the dose-response relationship an d time of exposure in relation to time of onset of LBP. There was inco nsistency of findings within and between studies relating to LBP. Howe ver, the evidence was consistently against a causal association betwee n smoking and sciatica/discal hernia. Conclusion: It cannot be clearly deduced whether smoking has a causal effect on LBP or whether the pos itive findings sometimes noted are linked to some other, still unident ified factor. However, there is clearly no proof supporting a causal a ssociation between smoking and sciatica/discal hernia.