The evaluating prescription opioid changes in veterans (EPOCH) study: Design, survey response, and baseline characteristics

Abstract

In the United States (US), long-term opioid therapy has been commonly prescribed for chronic pain. Since recognition of the opioid overdose epidemic, clinical practice guidelines have recommended tapering long-term opioids to reduced doses or discontinuation. The Effects of Prescription Opioid Changes for veterans (EPOCH) study is a national population-based prospective observational study of US Veterans Health Administration primary care patients designed to assess effects of evolving opioid prescribing practice on patients treated with long-term opioids for chronic pain. A stratified random sampling design was used to identify a survey sample from the target population of patients treated with opioid analgesics for ≥ 6 months. Demographic, diagnostic, visit, and pharmacy dispensing data were extracted from existing datasets. A 2016 mixed-mode mail and telephone survey collected patient-reported data, including the main patient-reported outcomes of pain-related function (Brief Pain Inventory interference; BPI-I scores 0-10, higher scores = worse) and health-related quality of life. Data on survey participants and non-participants were analyzed to assess potential nonresponse bias. Weights were used to account for design. Linear regression models were used to assess cross-sectional associations of opioid treatment with patient-reported measures. Of 14,160 patients contacted, 9253 (65.4%) completed the survey. Participants were older than non-participants (63.9 ± 10.6 vs. 59.6 ± 13.0 years). The mean number of bothersome pain locations was 6.8 (SE 0.04). Effectiveness of pain treatment and quality of pain care were rated fair or poor by 56.1% and 45.3%, respectively. The opioid daily dosage range was 1.6 to 1038.2 mg, with mean = 50.6 mg (SE 1.1) and median = 30.9 mg (IQR 40.7). Among the 73.2% of patients who did not receive long-acting opioids, the mean daily dosage was 30.4 mg (SE 0.6) and mean BPI-I was 6.4 (SE 00.4). Among patients who received long-acting opioids, the mean daily dosage was 106.2 mg (SE 2.8) and mean BPI-I was 6.8 (SE 0.07). Higher daily dosage was associated with worse pain-related function and quality of life among patients without long-acting opioids, but not among patients with long-acting opioids. Future analyses will use follow-up data to examine effects of opioid dose reduction and discontinuation on patient outcomes.

Fig 1. Study flow diagram.

Fig 2. Bothersome pain locations in the past 6 months among survey cohort participants (n = 9074).

Values are weighted percentages for each response option.

Fig 3. Density of mean daily dosage by opioid formulation (long-acting opioid versus no long-acting opioid) in 6 months before the index date among a) survey cohort patients and b) eligible patients.

Panel 3a: Survey cohort patients with daily dosage < 200 ME mg (n = 8946). Panel 3b: All eligible patients with daily dosage < 200 ME mg (n = 264,321). Blue = long-acting opioid; yellow = no long-acting opioid. Patients with daily dosage ≥ 200 ME mg are not shown. Panel 3a shows 8946 survey cohort participants with daily dose <200 ME mg (296 with a long-acting opioid and 11 without a long-acting opioid who had daily dosage ≥ 200 ME mg are not shown). Panel 3b shows 264,321 eligible patients with daily dose <200 ME mg (7217 with a long-acting opioid and 354 without a long-acting opioid who had daily dosage ≥ 200 ME mg are not shown).