title: Is smoking a risk factor for lumbar disc herniation?
abstract: OBJECTIVE
  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.
  
  
  CONCLUSIONS
  This systematic review demonstrates that smoking promotes the development of LDH.
authors.affiliation: Department of Orthopaedics, General Hospital of Jinan Military Commanding Region, Jinan, People's Republic of China.
authors.forename: Weimin
authors.initials: W
authors.lastname: Huang
authors.affiliation: Department of Endocrinology, General Hospital of Jinan Military Commanding Region, Jinan, People's Republic of China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Qian
authors.affiliation: Department of Orthopaedics, General Hospital of Jinan Military Commanding Region, Jinan, People's Republic of China.
authors.forename: Kai
authors.initials: K
authors.lastname: Zheng
authors.affiliation: Department of Statistics, General Hospital of Jinan Military Commanding Region, Jinan, People's Republic of China.
authors.forename: Lili
authors.initials: L
authors.lastname: Yu
authors.affiliation: Department of Orthopaedics, General Hospital of Jinan Military Commanding Region, Jinan, People's Republic of China. ever_23@sohu.com.
authors.forename: Xiuchun
authors.initials: X
authors.lastname: Yu
mesh_terms: D006801:Humans; D007405:Intervertebral Disc Displacement / Q000209:etiology*; D008159:Lumbar Vertebrae; D015233:Models, Statistical; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects*
keywords: Lumbar disc herniation; Meta-analysis; Review; Risk factors; Smoking; Systematic