Smoking and Risk of Surgical Site Infection after Spinal Surgery: A Systematic Review and Meta-Analysis

Background: The effect of smoking on the risk of surgical site infection (SSI) after spinal surgery remains controversial. Therefore, we conducted a meta-analysis to determine whether there is an association between smoking and the risk of SSI and to calculate the relative risk of infections attributable to smoking. Methods: We performed a literature search of cohort and case-control studies in the MEDLINE, Embase, and ISI Web of Science databases. Sensitivity and subgroup analyses were performed to test the robustness of overall estimates of risk and to investigate potential sources of heterogeneity. We further calculated the population-attributable fraction (PAF) to evaluate the proportion of SSIs associated with smoking. Results: In total, 26 independent observational studies involving 67,405 patients who underwent spinal surgery were analyzed. Smokers had a significantly higher risk of SSI than did nonsmokers (odds ratio [OR] 1.26; 95% confidence interval [CI] 1.05-1.51). Subgroup analysis according to the study design revealed an apparent association between smoking and SSI in the cohort subgroup (OR 1.40; 95% CI 1.17-1.66), but not in the case-control subgroup (OR 0.99; 95% CI 0.64-1.53). After evaluation of the PAF, the proportion of SSIs associated with smoking increased to 10.37%. Conclusions: This meta-analysis demonstrated that smoking increases the risk of SSI after spinal surgery. False-negative associations in other studies may have resulted from defects in the study design. However, because of the heterogeneity among the studies in the present meta-analysis, the results should be interpreted with caution.