Differential patterns of opioid misuse between younger and older adults - a retrospective observational study using data from South Carolina's prescription drug monitoring program.

Background: Most research on opioid misuse focuses on younger adults, yet opioid-related mortality has risen fastest among older Americans over age 55. Objectives: To assess whether there are differential patterns of opioid misuse over time between younger and older adults and whether South Carolina's mandatory Prescription Drug Monitoring Program (PDMP) affected opioid misuse differentially between the two groups. Methods: We used South Carolina's Reporting and Identification Prescription Tracking System from 2010 to 2018 to calculate an opioid misuse score for 193,073 patients (sex unknown) using days' supply, morphine milligram equivalents (MME), and the numbers of unique prescribers and dispensaries. Multivariable regression was used to assess differential opioid misuse patterns by age group over time and in response to implementation of South Carolina's mandatory PDMP in 2017. Results: We found that between 2011 and 2018, older adults received 57% ( p  < .01) more in total MME and 25.4 days more ( p  < .01) in supply, but received prescriptions from fewer doctors (-0.063 doctors, p  < 01) and pharmacies (-0.11 pharmacies, p  < 01) per year versus younger adults. However, older adults had lower odds of receiving a high misuse score (OR 0.88, p  < .01). After the 2017 legislation, misuse scores fell among younger adults (OR 0.79, p  < .01) relative to 2011, but not among older adults. Conclusion: Older adults may misuse opioids differently compared to younger adults. Assessment of policies to reduce opioid misuse should take into account subgroup differences that may be masked at the population level.