The Association between Stimulant, Opioid, and Multiple Drug Use on Behavioral Healthcare Utilization in a Safety-Net Health System

Abstract

Background

Prior studies show an association between drug use and healthcare utilization. The relationship between specific drug type and emergent/urgent, inpatient, outpatient and behavioral healthcare utilization has not been examined. We aimed to determine if multiple drug use was associated with increased utilization of behavioral healthcare.

Methods

To assess healthcare utilization, we conducted a retrospective cohort study of patients who accessed healthcare at a safety-net medical center and affiliated clinics. Using electronic health records, we categorized patients who used stimulants, opioids, or multiple drugs based on urine toxicology screening tests and/or International Classification of Diseases, 9^th Revision (ICD-9). Remaining patients were categorized as patients without identified drug use. Healthcare utilization by drug use group and visit type was determined using a negative binomial regression model. Associations were reported as incidence rate ratios. Utilization was described by rates of healthcare-related visits for inpatient, emergent/urgent, outpatient, and behavioral healthcare among patients who used drugs, categorized by drug types, compared to patients without identified drug use.

Results

Of 95,198 index visits, 4.6% (n=4,340) were by patients who used drugs. Opioid and multiple drug users had significantly higher rates of behavioral healthcare visits than patients without identified drug use (opioid incidence rate ratio [IRR]=7.2; 95% confidence interval [CI] 3.8–13.8; multiple drug use IRR=5.6, 95% CI 3.3–9.7). Patients who used stimulants were less likely to use behavioral health services (IRR=1.3, 95% CI 0.9–2.0) when compared to opioid and multiple drug users, but were more likely to use inpatient (IRR=1.6, 95% CI 1.4–1.8) and emergent/urgent care (IRR=1.4, 95% CI 1.3–1.5) services as compared to patients without identified drug use.

Conclusions

Integrated medical and mental healthcare and drug treatment may reduce utilization of costly healthcare services and improve patient outcomes. How to capture and deliver primary care and behavioral healthcare to patients who use stimulants needs further investigation.

INTRODUCTION

Drug involved people access costly healthcare resources more frequently than people who do not use drugs ^1–6. Utilization of costly healthcare resources by people who use drugs has been attributed to diseases associated with drug use such as infections and organ dysfunction ^1,7–14. Comorbid drug use and mental health disorders are highly correlated ^15–17. Individuals with mental health disorders may use drugs to self-medicate symptoms of depression or anxiety leading to poor health outcomes and use of costly healthcare resources ^17–20. People who use drugs with poorly controlled medical and mental health disorders have a great need to obtain routine healthcare, but often lack access ^21,22.

Traditionally, medical care, mental healthcare and drug treatment are provided in separate clinical sites. Among patients with HIV, the integration of addiction and HIV treatment improved antiretroviral adherence and HIV-related outcomes ^23–26. Linkage between medical, mental healthcare and drug treatment in patients with multiple comorbidities would improve the quality of care delivered while benefiting both patients and providers ^27,28. Service linkage can enhance patient compliance with medications and clinic appointments, allow for early identification of drug and alcohol use causing medical problems, and provide support for relapse prevention ^1,14,29–31.

This study examined healthcare utilization by drug type in a large patient cohort. We aimed to identify if drug use type (opioid, stimulant, multiple drug) was associated with specific healthcare-related service utilization (emergent/urgent, inpatient, outpatient, behavioral healthcare). Prior work has shown an association between polysubstance use, psychiatric symptoms, and mental health instability ^32,33. We hypothesized that patients who used multiple drugs would access behavioral health services more frequently than patients with monodrug use.

METHODS

Study Design and Setting

We conducted a retrospective cohort study of all patient visits to an urban safety-net medical center in 2010 (N=95,128). This study was approved by the Colorado Multiple Institutional Review Board. Denver Health Medical Center includes an emergency department, a 477-bed inpatient hospital, outpatient surgical and medical subspecialty clinics, and behavioral health and drug use disorder clinics. Denver Health Medical Center is affiliated with eight federally qualified community health centers located across Denver County which deliver primary care and women’s healthcare. Patients served are predominately uninsured and underinsured ethnic minorities ^34,35.

Data Source and Participants

All patient visits between January 2010 and December 2010 were examined via an electronic query of existing electronic health records (EHR) in the Denver Health Data Warehouse. The Data Warehouse pools retrospective data from both administrative and clinical applications used in medical care delivery and includes demographic and laboratory data, and International Classification of Diseases, 9^th Revision codes (ICD-9) ³⁶.

The first patient encounter during 2010 was categorized as the index visit. At the index visit, patients were categorized based on ICD-9 codes consistent with drug abuse/dependence in EHR data and on positive urine drug screens (UDS) in the four years preceding their index visit. Patients were then categorized as users of stimulants, opioids, or multiple drugs to identify drug-specific healthcare utilization patterns. Stimulant users included patients with at least one encounter with an ICD-9 diagnosis of stimulant abuse (305.6, 305.7) or dependence (304.2, 304.4) or a positive UDS for cocaine or amphetamine. Opioid users included patients with at least one encounter with an ICD-9 diagnosis of opioid abuse (305.5) or dependence (304.0) with or without a positive UDS for opioids. Patients with a positive UDS for opioids without an ICD-9 diagnosis indicating opioid abuse or dependence were excluded from the opioid use group since these patients might have been using opioids to treat pain-related diagnoses. They were instead described as patients without identified drug use. Multiple drug users were defined as patients with at least one encounter with an ICD-9 diagnosis indicating combinations of drug dependence or use (304.7, 304.8), or if they had at least one UDS positive for ≥ 2 drugs in the same UDS, or if they had ≥ 2 positive UDS for cocaine, amphetamine, and/or opioids on separate occasions during the four years prior to their index visit. All other patients were defined as patients without identified drug use. Drug use categories were mutually exclusive.

Baseline Measures

Sociodemographic characteristics came from registration data collected at the index visit. Chronic health conditions, mental health disorders, tobacco use, alcohol abuse/dependence, and prior drug abuse treatment were determined by querying visits in the four years preceding the index visit using ICD-9 codes (2006–2009).

Primary outcome variable: Utilization events

Follow-up visits were defined as utilization events and were determined for each patient in the 364 days following their index visit. Utilization events were categorized by drug use group (stimulant, opioid, multiple drugs, none identified). Utilization events included any healthcare visit subsequent to, but not including, the index visit, and were categorized by visit type (inpatient, emergent/urgent, outpatient, and behavioral health). Services offered in outpatient and community clinics included primary and subspecialty care. Behavioral health clinics offered mental health, drug, alcohol treatment, and opioid replacement therapy with methadone and buprenorphine. Pharmacotherapy for addiction treatment was not uniformly offered in outpatient or community clinics.

Statistical Analyses

Analyses were performed using SAS Enterprise Guide 4.3 (SAS Institute, Inc., Cary, North Carolina). Unadjusted associations between drug use groups and utilization events were assessed with one-way ANOVA or Kruskal Wallis test for continuous variables and chi-square test for categorical variables. Frequencies and proportions were reported for categorical data. Outcomes of interest found to be significant (p < 0.25) in the unadjusted analyses were included as covariates in the regression analyses. Healthcare utilization by drug use group and visit type was determined using a negative binomial regression model and associations were reported as incidence rate ratios. The multivariable (negative binomial) model was adjusted for age, gender, race/ethnicity, insurance status, tobacco use, mental health disorder and chronic health conditions. Mental health disorders identified included schizophrenia, bipolar, anxiety, depression, and personality disorders. Chronic health conditions identified included neoplasms, diabetes, hypertension, cardiac diseases, congestive heart failure (CHF), cerebrovascular disease, chronic obstructive pulmonary disease (COPD), end stage renal disease on dialysis, and HIV/AIDS. Utilization events by drug use groups were compared to patients without identified drug use with an incidence rate ratio (IRR) and a 95% confidence interval (95% CI).

RESULTS

Table 1 describes baseline characteristics. There were a total 95,198 index visits in 2010. There were 90,858 patients without identified drug use. Of these, females made up 54% (n=48,873) of the index visits, the majority of the visits were by Hispanics (42%, n=37,928), and the median age was 41±16 years. Ten percent (n=8,940) had current or prior alcohol use, and the combined total of all mental health disorders was 9% (n=8,351). The prevalence of past or present smoking was 13% (n=11,493), the most prevalent chronic health condition was hypertensive diseases (18%, n=16,405), and the combined total of all chronic health conditions was 26% (n=23,181).

Table 1.

Characteristics of All Patients with a Healthcare Visit (Inpatient, Emergent/Urgent, Outpatient, or Behavioral Health) during 2010 (N =95,198)^a

	Stimulant	Opioidsb	Multiple Drug	None Identified
Total	2,599	724	1,017	90,858
Sex, n (%)
Male	1,578 (61)	454 (63)	570 (56)	41,985 (46)
Female	1,021 (39)	270 (37)	447 (44)	48,873 (54)
Race, n (%)
Non Hispanic White	940 (36)	433 (60)	542 (53)	33,033 (36)
African American	723 (28)	59 (8)	147 (14)	13,281 (15)
Hispanic	853 (33)	210 (29)	294 (29)	37,928 (42)
Other or Unknown	83 (3)	22 (3)	34 (3)	6,615 (7)
Age (years)
Mean	42 ± 11	44 ± 13	43 ± 11	41 ± 16
Median	44	46	43	39
Insurance, n (%)
CICP/CHS*	785 (30)	151 (21)	218 (21)	21,891 (24)
Commercial	77 (3)	22 (3)	30 (3)	13,079 (14)
Medicare/Medicaid	1,165 (45)	191 (26)	396 (39)	26,497 (29)
Unknown	120 (5)	244 (34)	244 (24)	12,684 (14)
Self-Pay	452 (17)	116 (16)	129 (13)	16,707 (18)
Prior or Current Related Substance Abuse, n (%)
Drug Abuse Treatment	5 (0.2)	68 (9)	52 (5)	90 (0.1)
Alcohol Use	1,551 (60)	449 (62)	758 (75)	8,940 (10)
Alcohol Use and Mental Health Condition	808 (31)	178 (25)	544 (53)	1,727 (2)
History of Mental Health Disorder, n (%)
Schizophrenia	306 (12)	33 (5)	163 (16)	1,206 (1)
Bipolar	1,021 (39)	202 (28)	617 (61)	5,137 (6)
Anxiety	189 (7)	81 (11)	162 (16)	1,613 (2)
Depression	498 (19)	119 (16)	280 (28)	4,079 (4)
Personality Disorder	195 (8)	40 (6)	198 (19)	456 (0.5)
Combined Total of All Mental Health Disorders	1,304 (50)	270 (37)	706 (69)	8,351 (9)
History of Chronic Health Conditions, n (%)
Cancer	101 (4)	27 (4)	33 (3)	1,990 (2)
Diabetes	337 (13)	57 (8)	82 (8)	7,320 (8)
Hypertensive Diseases	956 (37)	198 (27)	302 (30)	16,405 (18)
Ischemic Heart Disease	223 (9)	34 (5)	54 (5)	2,404 (3)
Cardiomyopathy	153 (6)	27 (4)	33 (3)	1,439 (2)
Cerebrovascular Disease	98 (4)	18 (2)	27 (3)	1,130 (1)
COPD	609 (23)	133 (18)	223 (22)	6,934 (8)
HIV/AIDS	298 (11)	12 (2)	108 (11)	1,018 (1)
Dialysis	64 (2)	9 (1)	24 (2)	411 (0.4)
Combined Total of All Chronic Health Conditions	1,526 (59)	285 (39)	507 (50)	23,181 (26)
Past or Present Smoking	1,507 (58)	343 (47)	612 (60)	11,493 (13)

^aColorado Indigent Care Program requirements: Colorado resident or a migrant farm worker, and a citizen or legal immigrant; income/combined resources at or below 250% of FPL; not eligible for Medicaid

^bExcludes patients using opioids for chronic pain management (n = 969)

Among patients who used drugs (n=4,340), patients who used stimulants had the majority of the index visits 60% (n=2,599). Males predominated in each group and non Hispanic whites (NHW) comprised 36% (n=940) of stimulants users, 60% (n=433) of opioid users, and 53% (n=542) of multiple drug users. Comorbid alcohol use and mental health disorders were highly prevalent. Thirty-one percent (n=808) of patients who used stimulants, 25% (n=178) of patients who used opioids, and 53% (n=544) of patients who used multiple drugs had a dual diagnosis of alcohol abuse/dependence and mental health disorders. Fifty-nine percent (n=1,526) of stimulant users, 39% (n=285) of opioid users, and 50% (n=507) of multiple drug users had chronic health conditions.

Utilization Events (Inpatient, Emergent/Urgent, Outpatient, and Behavioral Healthcare)

Table 2 describes unadjusted and adjusted rates of utilization events among patients who used drugs as compared to patients without identified drug use. In the adjusted model, patients who used stimulants, opioids, or multiple drugs, were more likely to utilize both emergent/urgent and inpatient care as compared to patients without identified drug use. Patients who used opioids were less likely to utilize outpatient care (IRR 0.7, 95% CI 0.7–0.8) but more likely to access behavioral healthcare (IRR 7.2, 95% CI 3.8–13.8) as compared to patients without identified drug use (ref IRR=1). In the adjusted model, there were no differences in utilization of outpatient care among patients who used stimulants or multiple drugs as compared to patients without identified drug use. There was no difference in rate of behavioral healthcare visits among stimulant users as compared to patients without identified drug use.

Table 2.

Unadjusted^a and Adjusted^a, ^b Incidence Rate Ratios (95% CI) of Healthcare Visits among Drug Use Group as Compared to People without Identified Drug Use^c

	Stimulants		Opioids		Multiple Drug
	Unadjusted	Adjusted	Unadjusted	Adjusted	Unadjusted	Adjusted
Inpatient	3.0 (2.7, 3.4)	1.6 (1.4, 1.8)	2.2 (1.8, 2.8)	1.4 (1.1, 1.7)	2.8 (2.3, 3.4)	1.3 (1.1, 1.6)
Emergent/ Urgent	2.6 (2.4, 2.8)	1.4 (1.3, 1.5)	2.3 (2.0, 2.6)	1.4 (1.2, 1.6)	2.9 (2.5, 3.2)	1.5 (1.3, 1.7)
Outpatient	1.6 (1.5, 1.7)	1.1 (1.0, 1.2)	0.9 (0.8, 1.0)	0.7 (0.7, 0.8)	1.3 (1.2, 1.5)	0.9 (0.8, 1.0)
Behavioral Health	4.7 (2.9, 7.6)	1.3 (0.9, 2.0)	4.7 (1.9, 11.4)	7.2 (3.8, 13.8)	13.5 (6.4, 28.5)	5.6 (3.3, 9.7)

^aReference category: no identified drug use

^bAdjusted for age, gender, race/ethnicity, insurance, history of mental health disorder and/or alcohol use, history of cancer, diabetes, cardiac disease, cerebrovascular disease, COPD, HIV, smoking, and/or dialysis, using negative binomial regression.

^cBolded values are significant to p<0.05

Stimulant users had the highest rate of inpatient visits overall as compared to patients with opioid and multiple drug use (IRR 1.6, 95% CI 1.4–1.8). Stimulant users were least likely to obtain outpatient care as compared to patients with opioid or multiple drug use. In adjusted analyses, those who used opioids (IRR 7.2, 95% CI 3.8–13.8) and multiple drugs (IRR 5.6, 95% CI 3.3–9.7) were more likely to access behavioral healthcare as compared to patients who used stimulants (IRR 1.3, 95% CI 0.9–2.0).

DISCUSSION

Our results reiterate previous studies in which people who used drugs had higher utilization of costly emergent/urgent and inpatient services ^37–40. When examining utilization by specific drug type, patients who used multiple drugs accessed behavioral healthcare more frequently than stimulant users, but opioid users had the highest rate of behavioral healthcare utilization. This may be due, in part, to the fact that patients who used opioids could access both addiction and mental health treatment at our behavior health clinics. Patients who used stimulants had the lowest rate of behavioral healthcare utilization. This may be attributed to the lack of effective therapies to manage stimulant addiction, such as opioid replacement therapy used to treat opioid addiction. Patients who used stimulants may have had less incentive to obtain non-emergent behavioral healthcare on a regular basis. Prior studies demonstrated similar findings and showed that HIV infected people using stimulants were less likely to adhere to antiretroviral therapy as compared to HIV infected people using other drugs ^41–46. Identifying patients who use stimulants in the emergent/urgent and inpatient setting, and encouraging their participation in behavioral healthcare treatment, may reduce utilization of costly healthcare resources while improving patient outcomes.

Combining primary medical care, behavioral healthcare and substance abuse services to improve patient outcomes has been advocated for more than a decade ^{23,27,28,47,48}. Our findings also support an integrated healthcare delivery system. As shown here, patients who use opioids and multiple drugs are more likely to access behavioral healthcare services. By combining primary care and behavioral healthcare, we may be able to prevent costly healthcare utilization. A simple cellulitis due to injection drug use may be identified and treated early in the outpatient clinic if a patient, who injected drugs, were seen by a primary care provider immediately following their behavioral healthcare visit. Combined medical care and behavior healthcare delivery would potentially prevent the development of an abscess and a costly inpatient surgical procedure. Our findings demonstrate that this healthcare system, and others like it, represents a missed opportunity for primary care delivery to patients who use drugs and are already obtaining behavioral healthcare.

This study had some important limitations. There was likely underascertainment bias due to the use of ICD-9 codes and UDS to categorize patients into drug use groups. The use of ICD-9 codes to categorize drug use depends on the accuracy of the diagnosis and consistent provider documentation. Patients in this study may have received subsequent healthcare at another institution and would not be captured in our follow-up period. Missed outpatient and behavioral healthcare visits at outside institutions are less likely because Denver Health is the primary safety-net institution in Denver and is the only institution which accepts discount healthcare programs (CICP/DFAP) or Denver Health Medicaid within the county for follow-up care.

Our study population was largely comprised of non Hispanic Whites and African Americans with a significant burden of chronic medical and mental health disorders. These characteristics represent many patients seeking care in safety-net healthcare systems nationwide. Future research is needed to determine how best to deliver primary care and behavioral healthcare to patients who use stimulants and multiple drugs.