In this dissertation, we examined the impact of the NC MLIP on numbers of dispensed CS prescriptions and the dosages of opioids dispensed following release from the MLIP, providing important information on the sustained impacts of the program. Understanding
whether beneficiaries’ CS prescription fills and opioid dosages decreased, increased, or returned to similar levels following release from the MLIP, as compared to prior to MLIP enrollment, provides important information on larger program impacts. Moreover, comparing CS dispensing and opioid dosages following release from the MLIP to during MLIP-enrolled periods allowed us to examine the extent to which program impacts (i.e., overall reductions in dispensed CS prescriptions but increased out-of-pocket payments) were sustained or attenuated following release from the MLIP.
Additionally, we examined whether trajectories of beneficiaries’ dispensed opioid dosages differed across MLIP-related periods (i.e., prior to, during, and following release from the MLIP) for different strata of the beneficiary population. Our study was designed to extend previous work on underlying heterogeneity within populations of substance users and was the first to investigate potential heterogeneity of opioid dosage trajectories in a MLIP population. Findings from our trajectory analyses can be used to provide information that may help further focus the design of the MLIP by detecting attributes of beneficiaries who might need additional targeted intervention, such as increased case management services, complementary or alternative treatment approaches (e.g., physical therapy), and screening for medication-assisted therapy.
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Aim 1: Assess the impact of exposure to the NC MLIP on numbers of dispensed CS prescriptions and the dosages of opioids dispensed in the year following release from the MLIP. Using generalized estimating equations (GEE) to account for within-individual correlation over time, we examined numbers of dispensed CS prescriptions and dosages of opioids dispensed in the 12-month period following release from the MLIP, compared to a pre- MLIP period. We also estimated measures of association comparing the during MLIP enrollment period to a pre-MLIP period. While we expected that the MLIP had different impacts for
different types of beneficiaries across program periods (e.g., no change in CS use for some, decreased use for others), we hypothesized that we would observe the following average impacts described below.
Hypothesis 1a: On average, the number of CS prescriptions reimbursed by Medicaid and the dosage of opioids obtained from Medicaid-reimbursed prescriptions would be lower following release from the MLIP than prior to enrollment, but greater than during MLIP enrollment.
Hypothesis 1b: On average, the number of CS prescriptions not reimbursed by Medicaid and the dosage of opioids obtained from non-reimbursed prescriptions would be greater following release from the MLIP than prior to enrollment, but lower than during MLIP enrollment. Rationale: Analyses from the parent study suggested that some MLIP beneficiaries obtained some opioid and benzodiazepine prescriptions through out-of-pocket payments while in the MLIP; the extent to which this behavior persisted following release from the MLIP was unknown.
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Aim 2: Examine heterogeneity in beneficiaries’ trajectories of dispensed opioid dosages across periods prior to, during, and following release from the MLIP. Using latent class growth analyses, we estimated average opioid dosage trajectories across MLIP-related periods in order to approximate the underlying distribution of trajectories across the MLIP-enrolled
beneficiary population. We quantified and described detected patterns of longitudinal change, as well as the attributes of beneficiaries that were best captured by different trajectories.
Hypothesis: At least three trajectories of dispensed opioid dosages would be identified: a
trajectory that quickly declined during MLIP enrollment and remained low and stable, even post- MLIP; a trajectory that remained at a high but steady level across program periods with little change at program enrollment or disenrollment; and a trajectory that declined during MLIP enrollment and increased post-MLIP, however not to the same level as pre-MLIP. These trajectories were hypothesized to differ according to the following covariates: age, comorbidity burden, and recent history of mental health disorders, pain conditions, and substance use
32 Table 3. Overview of Dissertation Aims
Objective Data Analysis Overview
Overall
To examine
sustained impacts of a MLIP and to gain a detailed
understanding of heterogeneity in dispensed opioid dosages across periods prior to, during, and following release from the MLIP.
Linked NC Medicaid claims-NC CSRS records (i.e., PDMP data) was used for the period of 10/1/2009 through 6/30/2013 (3.75 years of data).
Data included persons enrolled in the MLIP at some point between 10/1/2010 (when the program started) through 9/30/2012.
Observational prospective cohort study design used. See cohort definitions below.
Aim 1 (Chapter 6)
Assess the impact of exposure to the NC MLIP on numbers of dispensed CS prescriptions and the dosages of opioids dispensed in the year following release from the MLIP.
Exposure: 12 months in the MLIP
Outcomes: number of opioid and benzodiazepine prescriptions dispensed per person per month (total #, # reimbursed by Medicaid, # not reimbursed by Medicaid); average daily dosage of opioids dispensed per person (in terms of average daily morphine milligram equivalents (MMEs)) (overall amount, amount obtained from Medicaid- reimbursed prescriptions, amount obtained from
prescriptions not reimbursed by Medicaid)
Covariates: age, sex, race, urbanicity of the beneficiary’s county of residence, overdose death rate in the beneficiary’s county of residence, Medicaid aid category, Medicaid class code, history of alcohol or other substance use-related disorders, history of medication-assisted treatment for opioid addiction, history of an overdose event, number of unique pharmacies visited, number of emergency department visits, number of inpatient admissions, history of
Cohort: independent living adults (e.g., excluded those living in skilled nursing facilities) between the ages of 18 and 64 years who were enrolled in the NC MLIP between October 2010 and September 2012. Followed from the first day of receiving any CS prescription (for outcome of CS dispensed) or opioid prescription (for outcome of MMEs dispensed) on or after October 1, 2009, throughout their period of lock-in, and up to one year following program release or until June 30, 2013,
whichever came first. To avoid conflating program effects for those who remained continuously enrolled in the MLIP and those who exited the MLIP
prior to completion,analyses
were restricted to those who remained in the MLIP for a full 12 months or were administratively censored in June 2013, the last month for which we had data.
Outcome measures (listed to the left) following MLIP
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In Chapter 4, we provide an overview of the methods used to fulfill these aims.
Additional details about the methods, as well as results and discussion of results can be found in Chapters 5-7.
To construct an appropriate cohort for Aim 1 and Aim 2 analyses, we conducted a detailed analysis of those eligible for, enrolled in, and retained in the NC MLIP. Chapter 5 is the
specific pain-related diagnoses (e.g., arthritis, back, neck, headache/migraine,
fibromyalgia, sickle cell), history of specific mental health-related diagnoses (e.g., depression, anxiety, bipolar, schizophrenia), Charlson comorbidity index, and temporal trend measures.
release and during MLIP enrollment were compared to those in a pre-MLIP
enrollment period
GEE were used to provide estimates of measures of association (e.g., count differences, count ratios).
Aim 2 (Chapter 7) Examine heterogeneity in beneficiaries’ trajectories of dispensed opioid dosages across periods prior to, during, and following release from the MLIP.
To examine dispensed opioid dosages, we calculated average daily MMEs of dispensed opioids (paid for using any payment source). For modeling purposes, we averaged each beneficiary’s average daily MMEs across each calendar month. We then log transformed this monthly average to obtain an approximately normal
distribution for improved model estimation. Trajectories were estimated across months prior to, during, and following release from the MLIP.
Latent classes were characterized by the covariates described above in Aim 1.
Cohort same as above (i.e., followed from first day of receiving any opioid prescription on or after October 1, 2009, throughout their period of lock-in, and up to one year following
program release or until June 30, 2013, whichever came first. Followed only those who remained in the MLIP for a full 12 months or were administratively censored in June 2013, the last month for which we had data).
Latent class growth analysis was used to disentangle and describe the number and shape of different trajectories of dispensed opioid dosages across periods prior to, during, and following release from the MLIP, as well as to characterize trajectory groups by important covariates.
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result of that analysis and was essential to informing cohort inclusion/exclusion criteria for Aim 1 and Aim 2 analyses (Chapters 6 and 7, respectively).
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CHAPTER 4 – METHODS