Medical detoxification for non-opioid substances is associated with lower likelihood of subsequent linkage to substance use disorder treatment

Abstract

Background:

While factors associated with completion of medical detoxification treatment for substance use disorders (SUD) are well described, there is limited information on barriers and facilitators to subsequent linkage to SUD treatment in the community. This study aimed to evaluate correlates of successful linkage to community SUD treatment on discharge.

Methods:

Data were drawn from two prospective cohorts of people who use unregulated drugs (PWUD) in Vancouver, Canada between December 2012 and May 2018. Multivariable generalized estimating equations were used to investigate factors associated with linkage to community SUD treatment in the six-month period after attending detoxification treatment.

Results:

Of the 264 detoxification treatment encounters contributed by 178 PWUD, these were most often (n=104, 39%) related to polysubstance use, and the majority (n=174, 66%) resulted in subsequent linkage to community treatment. In the multivariable analysis, compared to attending detoxification treatment for opioid use, attending detoxification treatment for stimulants (Adjusted Odds Ratio [AOR] = 0.23, 95% confidence interval [CI]: 0.10–0.51) and alcohol (AOR = 0.17, 95% CI: 0.06–0.54) were associated with lower odds of subsequent linkage to community treatment. Conversely, later calendar year of detoxification treatment remained associated with higher odds (AOR = 1.23, 95% CI: 1.06–1.42).

Conclusion:

Only two-thirds of detoxification treatment encounters in Vancouver were subsequently linked to community SUD treatment, with those related to non-opioid substances being less likely. Findings suggest the need for tailored interventions for specific substances to improve linkage to SUD treatment in the community on discharge.

1. INTRODUCTION

Healthcare systems around the world are increasingly challenged by the rising global burden of substance use disorders (SUD).¹ In 2017, the United Nations Office on Drugs and Crime estimated that 35 million people worldwide live with drug-related SUD resulting in unprecedented numbers of drug-related morbidity and mortality.² Alcohol consumption is also on the rise, disproportionally affecting high-income countries and accounting for 5.1% of the global burden of disease and injury.³ Altogether, drug and alcohol use disorders have caused an estimated 20 million disability-adjusted life years and 8.6 million years of life lost since 1980, with 305,800 deaths in 2016 alone.¹

Medical detoxification treatment, commonly referred as detox, provides medical stabilization to people with SUDs as they experience physical withdrawal related to cessation of substance use and is often coupled with interventions aimed to support these individuals with continued treatment once they complete detoxification treatment.⁴ Continuity of care with SUD treatment after attending detoxification treatment is associated with better health and social outcomes, including reduced likelihood of subsequent relapse to substance use, incarceration, homelessness, unemployment, and readmission to detoxification treatment.^4–6 However, rates of successful linkage to SUD treatment remain low due to a number of patient, program, and system-level barriers.^7–8 For instance, research has indicated that successful linkages to SUD treatment post detoxification treatment is more likely when the detoxification treatment facility is highly accredited, has fewer beds, is a shorter distance to outpatient treatment, is located in a larger city, and the individuals’ length of stay is longer.⁹ Individuals with timely follow-up (7–14d) to community SUD treatment after detoxification treatment also have better outcomes^6,10, as do individuals with shorter travel time to community SUD treatment.⁷

A number of interventions have been implemented in efforts to improve continuity of care after attending detoxification treatment including psychoeducational groups during detoxification treatment admission, outreach visits by nurses and patient navigators, as well as incentives and alerts as facilitators for community follow-up after discharge from detoxification treatment.^{7, 11–16} However, individual and social-structural factors impacting linkages are not well understood. Therefore, the objective of this study was to identify correlates of successful linkage to community SUD treatment after attending detoxification treatment among people who use drugs (PWUD) in Vancouver, Canada.

2. METHODS

2.1. Study design, procedures and population

This study used data from two ongoing and open prospective cohorts of PWUD in Vancouver, Canada. These cohorts have harmonized procedures for recruitment, follow-up, and data collection, and include the Vancouver Injection Drug Users Study (VIDUS) and the AIDS Care Cohort to Evaluate exposure to Survival Services (ACCESS), which began recruitment in 1996 and 2005, respectively. Individuals are recruited using community-based methods, including street outreach and self-referral, in neighborhoods that have high levels of unregulated substance use, homelessness, and criminalization. Eligibility criteria for both cohorts includes residing in the greater Vancouver region, unregulated drug use in the past month at the time of enrolment, as well as being 18 years of age or older. Additionally, VIDUS consists of individuals who are HIV-negative and have injected drugs in the month prior to enrolment, while ACCESS includes HIV-positive PWUD, who used drugs other than (or in addition to) cannabis in the month prior to enrolment. Recruitment and study procedures have been described in previous studies.¹⁷

At baseline, after providing informed consent, participants complete an interviewer-administered questionnaire and bloodwork (i.e., HIV and HCV serology and HIV clinical monitoring as appropriate), and subsequently complete follow-up questionnaires and bloodwork on a semiannual basis. The questionnaires gather information on participants’ sociodemographic characteristics, substance use patterns, healthcare access and utilization, and other relevant factors. Participants are given a CAD$ 40 honorarium at each study visit. Both the VIDUS and ACCESS studies have received approval by the University of British Colombia/ Providence Health Care Research Ethics Board.

For the present study, data from both cohorts were combined to achieve sufficient power to examine correlates of successful linkage to community SUD treatment after attending detoxification treatment. Questions regarding detoxification treatment were added to the questionnaire in December 2012. Therefore, the analytic sample was restricted to participants who reported attending detoxification treatment at least once between this date and May 2018. Specifically, individuals were included if they answered ‘yes’ to the question, “In the last six months, have you accessed detoxification treatment services for your drug or alcohol use?”

2.2. Measures

The primary outcome of interest was linkage to community addiction care in the six- month period subsequent to an interview each time the participant reported attending detoxification treatment. Community addiction care was defined as pharmacological treatment or counselling (individual or group).

The explanatory variables of interest included factors hypothesized to influence linkages to SUD treatment after detoxification treatment based on past literature.^7–9,14 Socio-demographic variables included age (per year older), gender (male vs. non-male), self-reported race/ethnicity (white vs. Black, Indigenous, or People of Color [BIPOC]), and highest level of education (not completed high school vs completed high school). We also included variables representing HIV status (positive vs. negative serology) and substance use-related factors, such as daily injection of substances (yes vs. no) and money spent on drugs (<CAD$ 50/day vs. ≥CAD$ 50/day). Social-structural variables included employment, Downtown Eastside (DTES) residency (a neighborhood characterized by high levels of poverty, homelessness, and substance use), incarceration, and homelessness. We also considered factors related to the detoxification treatment encounter, including reason for attending (enforced, convinced by supports [e.g., family, friends, doctor etc.], “other” reasons vs. wellness) and primary substance or substances of concern (stimulants, alcohol, or polysubstance use vs. opioids—illicit or prescribed), and calendar-year of detoxification treatment admission (per year increase). Except for the socio-demographic variables, which were time-fixed at baseline, all other variables were time-updated, and referred to the period where detox attendance was reported.

2.3. Statistical analyses

We initially described baseline characteristics of participants stratified by the substance for which they attended detoxification treatment. We used Pearson’s X² (or Fisher’s exact test in the presence of small cell counts) for categorical variables, and an ANOVA test was used for continuous variables. Then, we estimated the bivariable relationship between each explanatory variable and engagement with community addiction care after detoxification treatment. We used generalized estimated equations (GEE) with a logit-link function to account for the correlation of repeated measurements from the same participants over time. All variables with a p value ≤0.10 in the bivariate model were included in the final multivariate model. Lastly, to better estimate the impact of the declaration of the opioid-related public health emergency in British Columbia in April 2016, and consequent increases in the allocation of provincial resources to expand community access to opioid use disorder (OUD) treatment₁₈, we performed a sub-analysis treating calendar year of detoxification treatment admission as a dichotomous variable (≤2016 vs. >2016). The statistical software used for our analyses was R version 4.0.3, and p-values are two-sided.

3. RESULTS

Between December 2012 and May 2018, 178 participants enrolled in VIDUS/ACCESS reported attending detoxification treatment at least once and contributed 264 observations. Characteristics of the study sample are presented in Table 1. The median age was 43 years (Interquartile range [IQR] 35–50), and over half were male (n=108, 60.8%) and self-identified as BIPOC (n=109, 61.2%). At the interview where engagement in detox was reported, approximately half of the study sample (51.4%, n=92) were using injection drugs on a daily basis. The majority of the detoxification treatment visits were related to polysubstance use (n=104, 39%) followed by opioids (n=88, 33%). Among the 104 participants reporting detoxification treatment for polysubstance use, the vast majority (n=96, 92.3%) reported use of opioids in addition to another substance. During the study period, most participants attended detoxification treatment once (n=126, 70.8%), while some attended twice (n=32, 18.0%) and the remainder reported attending 3–7 times (n=20; 11.2%). As presented in Figure 1, 173 (66%) of the detoxification treatment encounters resulted in subsequent linkage to community treatment, with the majority of these (n=167, 96.5%) referring to pharmacological treatment.

Table 1.

Selected baseline characteristics of 178 people who attended detoxification treatment, stratified by primary substance of concern, Vancouver, Canada (2012–2018)

Characteristic	Total N (%) n=178	Opioid n (%) n=62	Stimulant n (%) n=35	Alcohol n (%) n=14	Polysubstance n (%) n=67	p – value
Socio-demographics
Age (median, IQR)	43 (35–50)	42 (35–48)	45(40–53)	47 (39–54)	40 (33–50)	0.085‡
Male gender	108 (60.8)	37 (59.7)	28 (80.0)	5 (35.7)	38 (56.7)	0.021†
White race	69 (38.8)	26 (41.9)	18 (51.4)	1 (7.1)	24 (35.8)	0.027†
High school education or higher	80 (44.9)	33 (53.2)	18 (51.4)	1 (7.1)	28 (41.8)	0.011†
Comorbidities
HIV+	76 (42.7)	23 (37.1)	19 (54.3)	10 (71.4)	24 (35.8)	0.060†
Substance use-related factors *
≥Daily injection	92 (51.4)	42 (70.0)	8 (32.0)	1 (7.1)	38 (56.7)	0.041†
CAD$ 50+ spent on drugs daily	87 (48.9)	31 (50.0)	12 (34.3)	5 (35.7)	39 (58.2)	0.084†
Social-Structural factors *
Employment	48 (27.0)	15 (24.2)	14 (40.0)	1 (7.1)	18 (26.9)	0.098†
DTES residency	123 (69.1)	43 (69.4)	19 (54.3)	9 (64.3)	52 (77.6)	0.110
Jail	17 (9.6)	4 (6.5%)	3 (8.6%)	0 (0)	10 (14.9)	0.278†
Homeless	69 (38.8)	24 (38.7)	13 (37.1)	3 (21.4)	29 (43.3)	0.505†
Detoxification-related
Reason for detoxification treatment						0.472†
Wellness	137 (77.0)	50 (80.7)	30 (85.7)	10 (71.4)	47 (70.2)
Enforced	7 (3.9)	1 (1.6)	1 (2.9)	1 (7.1)	4 (6.0)
Convinced by supports	4 (2.3)	1 (1.6)	1 (2.9)	1 (7.1)	1 (1.5)
Other	8 (4.5)	4 (6.5)	0 (0)	1 (7.1)	3 (4.5)

IQR, interquartile range; DTES, Downtown Eastside.

^*Refers to the 6-month period prior to the interview.

^†Fisher’s exact test.

^‡ANOVA.

Figure 1.

Linkage to community substance use disorder treatment after attending detoxification treatment among 264 unique detoxification treatment encounters in 178 people who use illicit drugs, Vancouver, Canada, 2012–2018

Table 2 shows the results of the unadjusted and adjusted GEE analysis of factors associated with linkage to community treatment. In the bivariate analysis, calendar year of detoxification treatment (odds ratio [OR] = 1.18, 95% confidence interval [CI]: 1.05–1.33) and daily injection use (OR = 2.15, 95% CI: 1.24–3.71) were positively associated with linkage to community treatment, while HIV infection (OR = 0.54, 95% CI: 0.30–0.98) and attending detoxification treatment for stimulants (OR = 0.20, 95% CI: 0.09–0.45) and alcohol (OR = 0.15, 95% CI: 0.05–0.42) relative to opioids as primary substance of concern were negatively associated. In the adjusted analysis, compared to attending detoxification treatment for opioid use, attending detoxification treatment for stimulants (adjusted odds ratio [AOR] = 0.23, 95% CI: 0.10–0.51) and alcohol (AOR = 0.17, 95% CI: 0.06–0.54) remained associated with significantly lower odds of subsequent linkage to community treatment, whereas later calendar year of detoxification treatment remained associated with higher odds of community treatment after detoxification treatment (AOR = 1.22, 95% CI: 1.06–1.41). In our sub-analysis, attending detoxification treatment after 2016 was associated with higher odds of linkage to community treatment (AOR = 1.74, 95% CI: 1.02–2.95).

Table 2.

Unadjusted and adjusted GEE analysis of factors associated with linkage to community substance use disorder treatment after attending detoxification treatment, Vancouver, Canada (2012–2018).

	Unadjusted		Adjusted‡
Characteristic	Odds Ratio (95% CI)	p – value	Odds Ratio (95% CI)	p – value
Socio-demographic
Age (per year older)	0.98 (0.95–1.01)	0.201
Male gender	1.41 (0.76–2.61)	0.275
White (vs. BIPOC)	1.20 (0.66–2.20)	0.552
High school education or higher	1.47 (0.81–2.66)	0.206
Comorbidities
HIV+	0.54(0.30–0.98)	0.042†	0.81 (0.43–1.53)	0.509
Substance use-related
Daily injection	2.15 (1.24–3.71)	0.006†	1.64 (0.93–2.90)	0.087
CAD$ 50+ spent on drugs daily	1.35 (0.80–2.29)	0.255
Social-structural *
Employment	1.25 (0.74–2.11)	0.407
DTES residency	1.32 (0.79–2.21)	0.285
Jail	1.67 (0.87–3.20)	0.122
Homeless	0.86 (0.51–1.46)	0.579
Detoxification-related
Primary substance of concern
Opioid	reference
Stimulant	0.20 (0.09–0.45)	0.001†	0.23 (0.10–0.51)	<0.001
Alcohol	0.15 (0.05–0.42)	0.001†	0.17 (0.06–0.54)	0.002
Polysubstance	0.81 (0.45–1.46)	0.486	0.82 (0.43–1.53)	0.528
Reason for detoxification treatment
Wellness	reference
Enforced	3.25 (0.67–15.77)	0.144
Convinced by supports	1.31 (0.60–2.87)	0.498
Other	0.94 (0.32–2.78)	0.907
Calendar-year of admission (per year increase)	1.18 (1.05–1.33)	0.007†	1.22 (1.06–1.41)	0.006

DTES, Downtown Eastside. CI, Confidence Interval

^*Refers to the 6-month period prior to the interview.

^†P < 0.10 and included in the multivariate model.

^‡Only the variables included in the final multivariable model are presented in this column.

4. DISCUSSION

This study found that between 2012 and 2018, two-thirds of detoxification treatment admissions reported by PWUD from a community-based cohort in Vancouver resulted in subsequent linkages to community SUD treatment, with those related to non-opioid substances being less likely to experience continuity of care. In addition, more recent detoxification treatment encounters were more likely to result in successful linkage to community SUD treatment.

Rates of post-detoxification treatment linkage to community SUD treatment have been found to vary widely but remain low in many settings₄. However, to our knowledge, there are no previous studies comparing the rates of successful linkage to community SUD treatment after detoxification treatment among individuals with different substances of primary concern. There are several possible reasons why individuals attending detoxification treatment for opioid use may have higher rates of linkages to post-detoxification treatment SUD care.

First, there is currently a heightened focus on the need for greater access to OUD treatment in the context of the ongoing opioid overdose crisis in the United States and Canada.¹⁹ Additionally, there are various effective pharmacological treatment options for OUD, some of which have been used clinically for several decades.^20–22 This contrasts with treatment for stimulant use disorder for which psychosocial interventions such as contingency management remain the first-line therapy. ^23–25 While effective medications for alcohol use disorder (AUD) also exist, unfortunately such pharmacotherapy is offered to a minority of patients, with a recent review finding that less than one in ten individuals who would benefit from these treatments are prescribed these.²⁶ Altogether, it may be the case that greater access to pharmacotherapy for OUD in the community, relative to other SUD, may partially account for our results.

As such, our findings suggest the need for tailored interventions for people presenting to detoxification treatment with specific substances of concern to improve linkage to SUD treatment in the community on discharge. For example, providing greater AUD treatment education to community clinicians may help improve linkage rates for individuals being admitted to detoxification treatment for AUD.²⁶ For people with stimulant use disorder, it may be beneficial for clinicians to stratify patients based on the desired function that is driving the stimulant use, in order to guide treatment options.²⁷ Additionally, addressing the various factors that prevent implementation of effective low-barrier, cost-efficient contingency management programs may help expand access for community stimulant use disorder treatment.^28–30 Further studies are required to assess substance-specific barriers and facilitators that influence individuals’ likelihood of receiving community SUD treatment after attending detoxification treatment, and, to assess whether tailored, substance-specific interventions while attending detoxification treatment results in improved outcomes..

Finally, our results highlight that people were more likely to be connected to community SUD treatment in more recent years. Perhaps this finding suggests that drawing on the growing evidence-base demonstrating improved patient outcomes with subsequent linkages to SUD care, detoxification treatment centers have evolved their policies to increasingly emphasize this as part of their discharge plans. Alternatively, as results from our sub-analysis suggest it may be the case that access to SUD care has been upscaled in the community setting as a result of the opioid-related public health emergency declared in BC in 2016.³¹ For instance, the number of opioid agonist treatment (OAT) providers in the province increased 61% between 2015 and 2021 (from 14,743 to 23,965). Perhaps these OAT providers are equipped with general SUD treatment competencies and may have contributed to an expanded community access to treatment for other SUD.

Findings from this study should be interpreted in light of some limitations. First, given that our sample was not randomly selected, our findings may not be generalizable to other populations of PWUD given the high degree of marginalization in Vancouver’s inner-city neighborhoods. Additionally, the eligibility criteria for both VIDUS and ACCESS includes unregulated drug use, therefore, people with heavy alcohol use who do not concurrently use illicit drugs were not considered. That said, undertreatment of AUD and stimulant use disorder is not unique to our study setting, but rather a global challenge. Therefore, we expect that addressing the underlying roots will contribute to improve linkage to community SUD treatment in any setting. Second, while studies have found that self-reported data from PWUD are reliable, there are still some known limitations such as response accuracy and bias.³²⁻³⁴ Lastly, the care provided in detoxification treatment facilities is not standardized and the location and quality of care received by participants is beyond the scope of this study.

In conclusion, this study found that two thirds of PWUD in our study were connected to community SUD treatment after attending detoxification treatment, with those attending detoxification services in more recent years being more likely. While this finding is encouraging, our results also showed that people who attended detoxification treatment for substances other than opioids were significantly less likely to have subsequent care than those who attended for opioid-related substances, suggesting the need for tailored-interventions to the primary substance of concern. Given the devastating health and social consequences associated with untreated SUD, optimizing linkages to community SUD treatment after detoxification treatment should be a public health priority.