Objectives The 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 setting A 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).
Participants Inpatients who were hospitalised to undergo elective surgery.
Primary and secondary outcome measures The 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.
Results Using 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, p<0.001). Similarly, smoking was significantly associated with postoperative 30-day mortality, with OR of 1.22 (95% CI 1.08 to 1.39, p=0.002).
Conclusions Our 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.
- public health
- smoking cessation
- post-operative complication
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Contributors RY designed the study, managed the data analysis and critically reviewed the manuscript. JK prepared the protocol and its statistical analysis plan and drafted the manuscript.
Funding This study was funded by Pfizer Japan.
Competing interests RY and JK are employees of Pfizer Japan.
Patient consent for publication Not required.
Ethics approval Approval by IRB/IEC was not required according to Japanese guidelines. The protocol and statistical analysis plan were internally approved by non-commercial medical peers before data acquisition from the database.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement All major results generated in this study and codes used for this study are shown in the published article or its online supplemental content. Raw data obtained from MVD Inc. are undisclosable due to contract between MDV Inc. and Pfizer Inc.
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