Semester

Spring

Date of Graduation

2019

Document Type

Dissertation

Degree Type

PhD

College

School of Public Health

Department

Epidemiology

Committee Chair

Robert M. Bossarte

Committee Co-Chair

Christa Lilly

Committee Member

Christa Lilly

Committee Member

Mike Brumage

Committee Member

Thomas Hulsey

Abstract

BACKGROUND AND OBJECTIVES: The United States is in the midst of an opioid overdose crisis and is now considered a public health emergency. Given the alarming rise in opioid overdose deaths, there is an urgent need to understand the characteristics and risks associated with opioid overdoses. The objectives of this study were 1) to compare factors associated with different type of opioid overdose, 2) to determine the conditional probability of repeat overdose among veterans with a prior overdose event and corresponding probability of mortality for each overdose event and, 3) to identify cause-specific mortality rate of those who experienced a nonfatal overdose during our study period. METHODS: Using clinical records and mortality files of more than 10.5 million veterans, we extracted data among those with a documented opioid overdose between January 1, 2011 and December 31, 2015. During this time, 13,333 veterans had at least one documented opioid overdose of any intent. RESULTS: Study 1. Patients who were younger in age (18-44 OR [odds ratio] 7.19, 45-64 OR 4.78) had significantly higher odds of a fatal index overdose and experiencing a repeat overdose (18-44 OR 2.13, 45-64 OR 1.78). Having one or more chronic pain diagnoses was both associated with experiencing a fatal index overdose (OR 3.96) or repeat overdose (OR 1.15). A diagnosis associated with mental health or substance abuse or dependence was significantly associated with experiencing a repeat overdose, (OR 1.54 and 1.25 respectively). Receipt of medication-assisted therapy (MAT) more than one year prior (OR 1.28) to the first (i.e. index) overdose was significantly associated with increased odds of a fatal overdose whereas receiving counseling services prior to index overdose was protective of experiencing a fatal index overdose. Study 2. One fifth of the study sample had a repeat overdose during the study period, with a conditional probability that increased linearly for each subsequent overdose event. The conditional probability of repeat overdose went from 21.1% on the second overdose to 43.2% for five or more overdoses. Mortality was highest among the first documented overdose. Study 3. Overall, veterans with a prior nonfatal overdose more often died from any cause in comparison to their veteran peers and had approximately 26 times the mortality rate to the general U.S. population. Veterans with a prior nonfatal overdose had a higher risk of death from substances (aHR [adjusted Hazard Ratio] 5.0, 95% CI [confidence interval]: 4.4-5.8), including a higher risk of death from drugs (aHR 6.9; 95% CI 5.8-8.1) and alcohol (aHR 2.7, 95% CI 2.1-3.6). For cause-specific mortalities assessed between veterans in our cohort and the general U.S. population, the standardized mortality rate ratio (SMR) was 114 times higher for deaths associated with substances (95% CI: 98.8-128.7), 107 times higher for deaths associated with hepatitis (95% CI: 65.5-152.7) and 68 times higher for deaths associated with liver cancers (95% CI: 47.9-88.7). Overall, veterans in our overdose cohort had an elevated mortality rate than the general public for all the specific causes of death assessed. CONCLUSION: Although risk factors for opioid overdoses are well studied, there appears to be differences between the type of opioid overdoses documented in a clinical setting. Given that mortality is highest on the first documented overdose suggests that prevention efforts should be further support to reach those patients at highest risk. Furthermore, given that the probability of iii experiencing a repeat overdose increases with each overdose event suggest that healthcare settings should be prepared to handle an influx in patients, specifically those with mental health diagnoses. Moreover, given the elevated risk of death from all-causes, specifically those associated with substances suggests the need for an integrated healthcare approach. Understanding risks factors, type of overdose, and cause-specific mortality among patients with an opioid overdose could help to inform healthcare interventions and potentially lead to better patient outcomes.

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