Prevalence of preoperative opioid usage and its impact on postoperative outcomes: a retrospective cohort study.

Preoperative opioid usage was one-tenth of the United States average. Despite its low prevalence and small dosage, preoperative opioid usage was associated with poor postoperative outcomes. Dedicated perioperative interventions to prevent opioid-associated adverse events should be developed even in countries with low opioid consumption.