title: Smoking cessation reduces postoperative complications: a systematic review and meta-analysis.
abstract: OBJECTIVE
  We aimed to review randomized trials and observational evidence to establish the effect of preoperative smoking cessation on postoperative complications and to determine if there is an optimal cessation period before surgery.
  
  
  METHODS
  We conducted a systematic review of all randomized trials evaluating the effect of smoking cessation on postoperative complications and all observational studies evaluating the risk of complications among past smokers compared with current smokers. We searched independently, in duplicate, 10 electronic databases and the bibliographies of relevant reviews. We conducted a meta-analysis of randomized trials using a random effects model and performed a meta-regression to examine the impact of time, in weeks, on the magnitude of effect. For observational studies, we pooled proportions of past smokers in comparison with current smokers.
  
  
  RESULTS
  We included 6 randomized trials and 15 observational studies. We pooled the 6 randomized trials and demonstrated a relative risk reduction of 41% (95% confidence interval [CI], 15-59, P = .01) for prevention of postoperative complications. We found that each week of cessation increases the magnitude of effect by 19%. Trials of at least 4 weeks' smoking cessation had a significantly larger treatment effect than shorter trials (P = .04). Observational studies demonstrated important effects of smoking cessation on decreasing total complications (relative risk [RR] 0.76, 95% CI, 0.69-0.84, P < .0001, I(2) = 15%). This also was observed for reduced wound healing complications (RR 0.73, 95% CI, 0.61-0.87, P = .0006, I(2) = 0%) and pulmonary complications (RR 0.81, 95% CI, 0.70-0.93, P = .003, I(2) = 7%). Observational studies examining duration of cessation demonstrated that longer periods of cessation, compared with shorter periods, had an average reduction in total complications of 20% (RR 0.80, 95% CI, 3-33, P = .02, I(2) = 68%).
  
  
  CONCLUSIONS
  Longer periods of smoking cessation decrease the incidence of postoperative complications.
authors.affiliation: Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario, Canada. Edward.mills@uottawa.ca
authors.forename: Edward
authors.initials: E
authors.lastname: Mills
authors.forename: Oghenowede
authors.initials: O
authors.lastname: Eyawo
authors.forename: Ian
authors.initials: I
authors.lastname: Lockhart
authors.forename: Steven
authors.initials: S
authors.lastname: Kelly
authors.forename: Ping
authors.initials: P
authors.lastname: Wu
authors.forename: Jon O
authors.initials: JO
authors.lastname: Ebbert
mesh_terms: D006801:Humans; D007902:Length of Stay; D008171:Lung Diseases / Q000209:etiology / Q000517:prevention & control; D019370:Observation; D011183:Postoperative Complications / Q000401:mortality / Q000517:prevention & control*; D016032:Randomized Controlled Trials as Topic; D018570:Risk Assessment; D012307:Risk Factors; D016540:Smoking Cessation / Q000706:statistics & numerical data; D013997:Time Factors; D014481:United States / Q000453:epidemiology; D014945:Wound Healing