Predictors of Long-Term Opioid Use After Opioid Initiation at Discharge From Medical and Surgical Hospitalizations

RESULTS

During FY 2011, 43,027 patients received an incident opioid prescription at discharge from a VHA hospital, including 26,476 surgical discharges and 16,551 medical discharges. Discharged veterans differed on nearly all the examined characteristics (Table 1). A lower proportion of surgical patients used VA mental health services, had a substance use disorder, anxiety, or depression diagnosis, or had active benzodiazepine or antidepressant prescriptions. A higher proportion of surgical patients had a chronic pain diagnosis. At discharge, a larger proportion of surgical patients (62.7%) than medical patients (48.6%) received hydrocodone and daily doses of ≥45 mg per day of morphine equivalents (12.8% vs 10.2%). Medical patients were more likely to receive an initial supply of ≥30 days.

The rate of LTO initiation was higher in medical patients (15.2%) than in surgical patients (5.3%; OR = 3.18; 95% confidence interval [CI], 2.97-3.41; Table 2). For reference, the rate of subsequent LTO initiation among outpatients was 19.3% (93,076 of 483,472). LTO use was most common among patients ages 50 to 64 years. Relative to urban areas, LTO risk was higher among residents of small, rural areas (OR = 1.29; 95% CI, 1.14-1.47). The interaction between inpatient service and race (χ² = 7.9; degrees of freedom = 2; P = .019) was significant; black race was associated with a reduced risk for LTO use in medicine service patients (OR = 0.77; 95% CI, 0.69-0.87) but not surgical patients (OR = 0.96; 95% CI, 0.83-1.13; Table 2).

Concurrent use of benzodiazepines, antidepressants, and muscle relaxants and chronic pain diagnosis (but not mental health clinic use and anxiety and depressive disorders) were associated with LTO use. Interactions with inpatient services were observed for substance use disorder diagnoses and prior nonopioid analgesic use; the magnitude of the association was higher among surgical service patients than in the medical patients model (Table 2).

Days’ supply was associated with LTO use in a dose-dependent fashion relative to the reference category of ≤7 days: OR of 1.24 (95% CI, 1.12-1.37) for 8 to 14 days; OR of 1.56 (95% CI, 1.39-1.76) for 15 to 29 days; and OR of 2.59 (95% CI, 2.35-2.86) for 30 days (Table 2). LTO risk was higher among patients with an estimated dose of ≥15 morphine equivalents per day (MED) compared with those with doses of <15 equivalents (OR = 1.11; 95% CI, 1.02-1.21); patients who received >45 MED were at the greatest risk (OR = 1.70; 95% CI, 1.49-1.94).

DISCUSSION

Our observed LTO use rate of 5.3% among surgical patients compares with rates of 0.12% to 1.41%⁵ and 5.9% to 6.5%¹² in privately insured samples and 4.1% among discharges in a single US hospital that included both medical and surgical patients in the United States.¹ The LTO use rate of 15.2% among medically discharged patients more closely resembles the rates found among outpatient initiators¹³ and lacks robust comparators.

The observation that subsequent LTO use occurs more frequently in discharged medical patients than surgical patients is consistent with the findings of Calcaterra et al.¹ that among patients with no surgery versus surgery during hospitalization, opioid receipt at discharge resulted in a higher adjusted OR (7.24 for no surgery versus 3.40 for surgery) for chronic opioid use at 1 year. One explanation for this finding may be an artifact of cohort selection in the study design: patients with prior opioid use are excluded from the cohort, and prior use may be more common among surgical patients presenting for elective inpatient surgery for painful conditions. Previous work suggests that opioid use preoperatively is a robust predictor of postoperative use, and rates of LTO use are low among patients without preoperative opioid exposure.⁶

Demographic characteristics associated with persistent opioid receipt were similar to those previously reported.^5,8,9 The inclusion of medication classes indicated in the treatment of mental health or pain conditions (ie, antidepressants, benzodiazepines, muscle relaxants, and nonopioid analgesics) resulted in diagnoses based on ICD-9 codes being no longer associated with LTO use. Severity or activity of illness, preferences regarding pharmacologic or nonpharmacologic treatment and undiagnosed or undocumented pain-comorbid conditions may all contribute to this finding. Future work studying opioid-related outcomes should include variables that reflect pharmacologic management of comorbid diagnoses in the cohort development or analytic design.

The strongest risk factors were potentially modifiable: days’ supply, dose, and concurrent medications. The measures of opioid quantity supplied are associated with subsequent ongoing use and are consistent with recent work based on prescription drug–monitoring data in a single state¹⁴ and in a nationally representative sample.¹⁵ That this relationship persists following hospital discharge, a scenario in which LTO use is unlikely to be initiated by a provider (who would be expected to subsequently titrate or monitor therapy), further supports the potential to curtail unintended LTO use through judicious early prescribing decisions.

We assessed only opioids that were supplied through a VA pharmacy, which may lead to the misclassification of patients as opioid naive for inclusion and an underestimation of the rate of opioid use following discharge. It is possible that differences in the rates of non-VA pharmacy use differ in medical and surgical populations in a nonrandom way. This study was performed in a large, integrated health system and may not be generalizable outside the VA system, where more discontinuities between hospital and ambulatory care may exist.