Is smoking a risk factor for lumbar disc herniation?

PURPOSE: To evaluate the association between cigarette smoking and lumbar disc herniation (LDH). METHODS: Cohort or case-control studies were identified by searches of several data bases, including Pubmed, Embase, Web of Science, and BIOSIS, for entries made up to December 2014. Data extraction was performed by two independent investigators. The data synthesis was performed using the random effects model. Subgroup analysis, sensitivity analyses, and assessment for publication bias were also performed. RESULTS: This systematic review included 12 studies-six each of cohort and case-control studies. The combined reported values showed that the relative risk of the association between smoking and LDH was 1.27 [95 % confidence interval (CI), 1.15-1.40] overall, 1.48 (95 % CI, 1.27-1.73) for case-control studies, and 1.17 (95 % CI, 1.05-1.30) for cohort studies. CONCLUSION: This systematic review demonstrates that smoking promotes the development of LDH.