Data source and study population

The study involved a retrospective analysis of claims data from the OptumLabs Data Warehouse (OptumLabs), which includes de-identified claims data for commercial and Medicare Advantage enrollees in a large, private, US health plan. The commercial population includes people who receive healthcare coverage through their or a family member’s employer or who purchase coverage on the individual market. The Medicare Advantage group includes people who qualify for public insurance owing to age (≥65 years) or long term disability; people eligible for Medicare have the choice of enrolling in coverage directly from the government (known as fee-for-service Medicare) or from private companies in a program called Medicare Advantage. As of 2017, 33% of Medicare beneficiaries opted for Medicare Advantage coverage.25

OptumLabs contains longitudinal health information on enrollees, representing a diverse mixture of ages, ethnicities, and geographic regions across the US; see appendix A for a comparison of the OptumLabs population with the broader insured US population. The health plan provides comprehensive insurance coverage for physician, hospital, and prescription drug services. We used data from January 1, 2009 through June 30, 2018, with a last day of surgery being December 31, 2017 to account for required follow-up.

We identified 20 commonly performed surgical procedures including seven common general surgery procedures (laparoscopic cholecystectomy with or without intraoperative cholangiogram, minimally invasive inguinal hernia repair, open inguinal hernia repair, simple mastectomy without reconstruction, breast lumpectomy with or without axillary node biopsy, pancreaticoduodenectomy (Whipple), and parathyroidectomy), six orthopedic operations (carpal tunnel release, knee arthroscopic minesectomy, rotator cuff surgery, total knee replacement, total hip replacement, and lumbar laminotomy or laminectomy via posterior approach), two colorectal procedures (minimally invasive low anterior resection with or without ostomy and partial colectomy with or without ostomy), two urology procedures (minimally invasive partial or total nephrectomy and minimally invasive prostatectomy), and two thoracic procedures (open lung lobectomy and video assisted thoracoscopic lung wedge), as well as minimally invasive hysterectomy. We chose the procedures with the aim of including common inpatient and outpatient procedures across multiple specialties and spanning varying degrees of expected postoperative pain. The array of surgeries allows us to assess the extent to which characteristics of discharge prescription are related to expected pain after surgery.

To reduce confounding as much as possible, we constructed a cohort with minimal clinical complexity. We excluded patients who were taking opioids before surgery—defined as patients who had filled no prescriptions for opioids in the previous six months—as well as those who may be in treatment for opioid use disorder by requiring no buprenorphine or methadone in the 90 days after surgery. In addition, we included only patients with at least six months of continuous enrollment in both medical and prescription coverage before surgery. To limit the clinical complexity of the cohort, we excluded patients having multiple unrelated procedures on the same day (see appendix B), those with an inpatient stay longer than seven days, and those admitted as an inpatient more than one day before surgery was performed. We excluded patients receiving non-cancer surgeries if they had cancer, as well as any patients receiving hospice services. To ensure that we were capturing post-surgery opioid fills, we limited the sample to patients who were discharged home and did not have a stay in a skilled nursing facility within a day of discharge (surgery date for those who were not admitted as inpatients). Finally, we required 90 days of insurance enrollment after surgery to ensure that patients survived surgery when we evaluated continued opioid use. See appendix C for the cohort flow chart.

We summarized discharge prescriptions into one of five mutually exclusive and collectively exhaustive categories: no opioid fill, any long acting opioid (with or without any short acting opioid, including tramadol), tramadol only, a short acting opioid other than tramadol alone (reference group), or tramadol plus another short acting opioid. Throughout, we use the “tramadol only” category to interpret tramadol findings, as people who receive multiple opioids at discharge may be different in important, unobserved ways. We followed patients until they were censored by one of the following events: the end of the study period (June 30, 2018); disenrollment from insurance; or another surgery, as defined by a claim for an anesthesia service (see supplementary methods for a list of CPT (current procedural terminology) codes used).

The analysis of discharge prescriptions included patients with at least 30 days of uncensored follow-up who had an opioid fill of less than 1400 morphine milligram equivalents (MME; excludes top 0.5% of discharge fills). The analyses of chronic opioid use included patients with any post-surgery opioid fill and at least 180 days of uncensored follow-up. All patients in all analyses had at least 90 days of post-surgery insurance coverage, which was used to ensure that patients had survived surgery. Patients included in the main outcome analyses had 180 days with no further surgeries, in addition to having insurance coverage during that time.