The Effect of Smoking on the Risk of Sciatica: A Meta-analysis

BACKGROUND: The role of smoking in sciatica is unknown. This study aimed to estimate the effect of smoking on lumbar radicular pain and clinically verified sciatica. METHODS: Comprehensive literature searches were conducted in PubMed, Embase, Web of Science, Scopus, Google Scholar, and ResearchGate databases from 1964 through March 2015. We used a random-effects meta-analysis, assessed heterogeneity and publication bias, and performed sensitivity analyses with regard to study design, methodological quality of included studies, and publication bias. RESULTS: Twenty-eight (7 cross-sectional [n = 20,111 participants], 8 case control [n = 10,815], and 13 cohort [n = 443,199]) studies qualified for a meta-analysis. Current smokers had an increased risk of lumbar radicular pain or clinically verified sciatica (pooled adjusted odds ratio [OR] 1.46; 95% confidence interval [CI], 1.30-1.64, n = 459,023). Former smokers had only slightly elevated risk compared with never smokers (pooled adjusted OR 1.15; 95% CI, 1.02-1.30, n = 387,196). For current smoking the pooled adjusted OR was 1.64 (95% CI, 1.24-2.16, n = 10,853) for lumbar radicular pain, 1.35 (95% CI, 1.09-1.68, n = 110,374) for clinically verified sciatica, and 1.45 (95% CI, 1.16-1.80, n = 337,796) for hospitalization or surgery due to a herniated lumbar disc or sciatica. The corresponding estimates for past smoking were 1.57 (95% CI, 0.98-2.52), 1.09 (95% CI, 1.00-1.19), and 1.10 (95% CI, 0.96-1.26). The associations did not differ between men and women, and they were independent of study design. Moreover, there was no evidence of publication bias, and the observed associations were not due to selection or detection bias, or confounding factors. CONCLUSIONS: Smoking is a modest risk factor for lumbar radicular pain and clinically verified sciatica. Smoking cessation appears to reduce, but not entirely eliminate, the excess risk. (C) 2016 Elsevier Inc. All rights reserved.