Effects of active smoking on postoperative outcomes in hospitalised patients undergoing elective surgery: a retrospective analysis of an administrative claims database in Japan

ObjectivesThe purpose of this study was to investigate the effects of smoking on prognosis after elective surgeries. Incidence of 30-day postoperative complications was compared between propensity score-matched ‘ever-smoker’ and ‘never-smoker’ cohorts. Thirty-day mortality and medical costs during the hospital stay were also compared.Design and settingA large-scale retrospective study using deidentified administrative claims data obtained from 372 acute care hospitals across Japan using the Diagnosis Procedure Combination system (ie, a flat-fee payment system).ParticipantsInpatients who were hospitalised to undergo elective surgery.Primary and secondary outcome measuresThe primary endpoint of this study was incidence of 30-day postoperative complications. Secondary endpoints were 30-day mortality and total medical costs during hospitalisation. Comparison between ever-smokers and never-smokers was conducted using matched cohorts created by 1:1 propensity score matching.ResultsUsing 561 598 eligible patients, matched ever-smoker and never-smoker cohorts (n=1 55 593 each) were created. Ever-smokers were defined as patients with Brinkman Index ≥1. The percentage of patients who were male was 76.7%, and mean ages for ever-smokers and never-smokers were 65.1±13.8 years old and 66.4±15.3 years old, respectively. The Brinkman Index of the ever-smoker cohort was 677.6±553.4. Smoking was significantly associated with higher risk of 30-day postoperative complications compared with not smoking (OR 1.15, 95% CI 1.13 to 1.17, pConclusionsOur results suggest that smoking could be associated with risk of poor postoperative outcomes. In particular, a history of smoking may increase the risk of 30-day postoperative complications as well as that of 30-day mortality. The results suggest that smoking might have a harmful effect on postoperative outcomes irrespective of types of surgery.