Abstract
Illicit drug injection typically occurs in private or semi-public settings where two or more injectors are present. In a large sample of young adult injectors (aged 15–30) in five US cities, we describe those who reported consistently injecting by themselves in a recent period. Among 3,199 eligible subjects, 85% were male, median age was 24 years, and median number of years injecting was four. Fifteen percent (n=467) who reported always injecting alone in the previous three months were compared to other IDUs to understand the relationship between this practice and injection risk behavior. IDUs who reported injecting alone were substantially less likely to report injection with a syringe (AOR=0.16, 95% CI 0.1–0.2) or other drug preparation equipment (AOR=0.17, 95% CI 0.13–0.2) previously used by another injector. Markedly low rates of injection risk behavior were observed in IDUs who reported injecting alone; this practice may facilitate safe injection by granting the individual greater control over the injection setting. However, risks may include accidental overdose with severe consequences.
1. Introduction
Illegal drug injection often occurs in groups of two or more injectors (Koester et al., 2005; Curtis et al., 1995). Injections occurring in the presence of others may take place in private or semi-public injection settings such as abandoned buildings or “squats” or among individuals who have pooled their money to buy and inject drugs together, which often involves sharing the same syringe (Neaigus et al., 1994). Preparation of drugs for injection is a somewhat complex, multi-step process requiring attention both to avoid loss or waste of expensive drugs and to avoid cross-contaminating syringes and other injection equipment via contact with the blood of others. Cross-contamination of syringes, drug cookers and filtration “cottons” has been implicated in the transmission of hepatitis C virus (HCV); descriptive data suggest that substantial exposure to blood may occur via tourniquets or surfaces where injection or drug preparation occurs (Hagan et al., 2001; Hahn et al., 2002; Thorpe et al., 2002; van Beek et al., 1994).
Ethnographic studies suggest that IDUs may choose to inject alone for several reasons: to avoid sharing drugs; to avoid peer pressure to share their syringes or other injection equipment; or to obviate the need to closely monitor whether other IDUs might contaminate their drug solution or injection equipment (Koester et al., 2005). IDUs who wish to keep their drug use private to avoid possible legal and social consequences may also inject alone as may IDUs who are socially isolated from peers or intervention programs. For other injectors, lack of resources to acquire drugs may limit opportunities to inject alone. This paper describes injecting alone in a large sample of young adult IDUs in five US cities to understand characteristics associated with injecting alone and to examine whether this practice is associated with safer or riskier injection practices. These findings may be helpful for informing the development of intervention programs aimed at reducing harms associated with injection drug use.
2. Methods
The Collaborative Injection Drug Users Study III/Drug User Intervention Trial (CIDUS III/DUIT) was a randomized controlled trial of a behavioral intervention to reduce HIV and HCV infection among young IDUs (Garfein et al., 2006). Eligible individuals were 15–30 years old and reported injection of any illicit drug in the previous six months. Participants were recruited in Baltimore, Chicago, Los Angeles, New York City and Seattle through street and agency outreach, targeted advertising, and respondent-driven recruitment. At the baseline study visit, eligible subjects completed a risk behavior interview via audio computer-administered self-interview (ACASI) followed by a blood draw and counseling and testing for HIV and HCV antibody. HCV antibody testing was performed using an enzyme immunoassay (EIA) test (Abbott Laboratories EIA 2.0 (Chicago, IL), or Ortho Diagnostic Systems EIA 3.0 (Raritan, NJ)). Reactive specimens were retested in duplicate using EIA and were interpreted as anti-HCV positive if either or both specimens were reactive. HIV antibody testing was performed using standard ELISA screening and Western blot confirmation. Total HBV core antibody (anti-HBc) testing was done with CORAB (Abbott Laboratories, Abbott Park, IL).
The questionnaire asked about risk behavior in the previous three-month period, including whether the participant had injected with a syringe previously used by another IDU and about using drug injection or preparation equipment (cookers, “cottons”, and rinse water) together with other IDUs, or using equipment previously used by another injector. Wording of the questions was intended to include the possibility of injecting alone using potentially contaminated syringes or other equipment, e.g., “Even though you were always alone when you injected, did you even once use a needle that someone else had used before you?”. Participants were also asked whether they had consistently injected by themselves during the previous three months – the wording of the question was, “In the last three months, did you ever inject with people who were injecting at the same time you were?”.
General knowledge of hepatitis and HIV natural history was assessed using eight true/false questions; the number of correct answers were summed to create a general knowledge score (Cronbach alpha=0.7). Knowledge of hepatitis and HIV transmission risk was assessed using thirteen true/false questions, and the number of correct answers were summed to create a risk knowledge score (Cronbach alpha=0.7). To understand underlying psychological factors influencing risk behavior in participants, the Rosenberg Self Esteem scale was included in the assessment (Cronbach alpha=0.9) (Rosenberg, 1989). Depression was measured using the Brief Symptom Inventory (Cronbach alpha=0.9) (Derogatis and Milisaratos, 1983). The questionnaire also asked about peer norms related to injection risk behavior (e.g., the proportion of their friends who inject with syringes previously used by other IDUs). The study was reviewed and approved by the institutional review boards of the US Centers for Disease Control and Prevention and the individual study sites.
In this analysis, we describe IDUs who report consistently injecting alone during the three months prior to study enrollment; sociodemographic characteristics and drug use, drug treatment, and incarceration histories were compared using chi-square and t-test statistics. A multivariate model was used to examine which of these characteristics were independently associated with injecting alone; stepwise selection was used to choose variables to include in an exploratory model. The second part of the analysis examined whether injecting alone was associated with safer injection in terms of possible exposure to blood-borne viruses via the use of syringes or other drug preparation equipment previously used by another IDU. While we hypothesized that injecting alone was likely to be associated with safer injection, it was conceivable that IDUs could obtain injection equipment previously used by another injector and then inject by themselves. Multivariate logistic regression modeling examined the strength of the association between injecting alone and these drug injection practices, adjusting for other factors found to be associated with injecting alone (age, race, homelessness, injection frequency and history of drug treatment or needle exchange use). Black tar heroin was included in the multivariate model examining use of drug preparation equipment used by another injector because it is a semi-solid material and must be heated (in a cooker) to form a solution that can be evenly divided among injectors; as such, its use was expected to be associated with injecting drugs with one or more persons. Unadjusted associations between injecting alone and contextual, psychological and knowledge variables were examined in univariate analysis to characterize this unique subgroup of IDUs.
3. Results
3.1 Characteristics of IDUs who consistently injected alone during the past 3 months
Of the 3,285 IDUs enrolled in the study; 71 were excluded from this analysis because they had not injected in the past 3 months, and 15 were excluded because of missing data regarding recent injection behavior. Among the remaining 3,199 IDUs, 467 (14.6%) reported that they had always injected alone during the past 3 months (Table 1). Eighty-five percent of subjects were male, median age was 24 years, and the median number of years since first injection was four. The majority of subjects were white (64%), 17% were Hispanic, 7% black, and 11% of other race/ethnicity.
Table 1.
Descriptive characteristics of injection drug users who always injected alone in the past 3 months vs. other participants in the CIDUS III/DUIT Study1 of young injectors in 5 US cities
| Baseline characteristics
|
Always injected alone in the past 3 months | ||||
|---|---|---|---|---|---|
| Yes (n=467) | No (n=2732) | ||||
| n | % | n | % | p | |
| Sex | <0.01 | ||||
| Male | 356 | 16.0% | 1867 | 84.0% | |
| Female | 111 | 11.4% | 865 | 88.6% | |
| Age, years | <0.01 | ||||
| 15–19 | 40 | 9.7% | 374 | 90.3% | |
| 20–24 | 178 | 12.6% | 1232 | 87.4% | |
| 25–30 | 249 | 18.1% | 1126 | 81.9% | |
| Race/ethnicity | <0.01 | ||||
| Hispanic | 113 | 21.4% | 415 | 78.6% | |
| Black, non-Hispanic | 69 | 29.4% | 166 | 70.6% | |
| White, non-Hispanic | 241 | 11.8% | 1810 | 88.2% | |
| Other, non-Hispanic | 42 | 11.7% | 316 | 88.3% | |
| Study site | <0.01 | ||||
| Baltimore | 134 | 14.0% | 822 | 86.0% | |
| Chicago | 119 | 15.2% | 663 | 84.8% | |
| Los Angeles | 70 | 13.5% | 450 | 86.5% | |
| New York City | 85 | 23.1% | 283 | 76.9% | |
| Seattle | 59 | 10.3% | 514 | 89.7% | |
| Education | <0.01 | ||||
| ≤ 11th grade | 220 | 17.7% | 1025 | 82.3% | |
| High School graduate/GED2 | 245 | 12.6% | 1705 | 87.4% | |
| Usual income | 0.02 | ||||
| Legal source | 382 | 15.3% | 2108 | 84.7% | |
| Illegal source | 81 | 11.8% | 608 | 88.2% | |
| Homeless | <0.01 | ||||
| No | 340 | 18.0% | 1550 | 82.0% | |
| Yes | 126 | 9.7% | 1174 | 90.3% | |
| Residence | |||||
| Parents’ place | 165 | 15.4% | 904 | 84.6% | NS |
| Own/someone else’s place | 151 | 14.7% | 876 | 85.3% | |
| Other less stable place | 145 | 13.3% | 943 | 86.7% | |
| Ever used needle exchange programs | <0.01 | ||||
| No | 230 | 17.5% | 1086 | 82.5% | |
| Yes | 225 | 12.3% | 1607 | 87.7% | |
| Ever incarcerated | 0.02 | ||||
| No | 142 | 17.0% | 695 | 83.0% | |
| Yes | 325 | 13.8% | 2037 | 86.2% | |
| Ever in drug treatment | <0.01 | ||||
| No | 248 | 17.9% | 1139 | 82.1% | |
| Yes | 219 | 12.1% | 1587 | 87.9% | |
| Injection frequency | <0.01 | ||||
| Less than daily | 269 | 18.7% | 1171 | 81.3% | |
| Daily | 198 | 11.3% | 1561 | 88.7% | |
| Years since first injection | NS | ||||
| 0–3 | 196 | 15.0% | 1110 | 85.0% | |
| 4+ | 264 | 14.1% | 1608 | 85.9% | |
| Primary drug injected | NS | ||||
| Heroin | 330 | 14.8% | 1899 | 85.2% | |
| Heroin with cocaine | 53 | 13.5% | 339 | 86.5% | |
| Amphetamines | 38 | 12.4% | 269 | 87.6% | |
| Cocaine, crack, other | 25 | 14.6% | 146 | 85.4% | |
| Black tar heroin was primary drug injected (alone or in combination) | <0.01 | ||||
| No | 358 | 15.8% | 1904 | 84.2% | |
| Yes | 85 | 10.4% | 736 | 89.6% | |
Collaborative Injection Drug User Study III/Drug User Intervention Trial Study
GED = General Equivalency Diploma
Men were more likely than women to report that they always injected alone in the past 3 months (16% vs. 11% of women). Those who were older than 25 years, Hispanic or black, or lived in New York City were also more likely to report always injecting alone, as were those participants who had a legal source of income or had not finished high school. Homeless subjects were less likely to inject alone, as were those who had ever used a needle exchange or been incarcerated or in a drug treatment program. Those who injected at least once per day were less likely to inject alone (11% vs. 19% of those who injected less often, p<0.01). There was no association between injecting alone and years since first injection or primary injected drug. Black tar injectors were less likely to report always injecting alone in the past three months.
Those who injected alone were substantially more likely to report that they mostly injected at their parent’s home or their own place (43%) compared to other IDUs (30%) (Table 2). IDUs who injected with others were more likely to report injecting in public settings, such as cars, streets, parks or abandoned buildings than did those who injected alone (46% vs. 34%). Those who injected alone were substantially less likely to report having a sex partner who injects (25% vs. 51%). Those who injected alone were also less likely to report using many other non-injected drugs such as marijuana, inhalants, hallucinogens, tranquilizers, street methadone, crack or other cocaine, or methamphetamine. Non-injection use of heroin was reported by the same proportion of subjects in each group (74–75%), and heroin was the primary injection drug for the majority of participants (70%).
Table 2.
Contextual, psychosocial and serological characteristics of injection drug users who always injected alone in the past 3 months vs. others, CIDUS III/DUIT Study1
| Always injected alone in the past 3 months | |||||
|---|---|---|---|---|---|
| Yes (n=467) | No (n=2732) | ||||
| n | % | n | % | p | |
| Primary injection setting | <0.01 | ||||
| Parent’s place | 92 | 20.0% | 372 | 13.7% | |
| Own place | 105 | 22.8% | 439 | 16.2% | |
| Friend/partner’s | 78 | 17.0% | 515 | 19.0% | |
| Dealer’s place | 10 | 2.2% | 75 | 2.8% | |
| Car/vehicle | 44 | 9.6% | 471 | 17.4% | |
| Public streets, parks | 67 | 14.6% | 493 | 18.2% | |
| Abandoned bldg | 43 | 9.3% | 314 | 11.6% | |
| Other | 21 | 4.6% | 35 | 1.3% | |
| Had an injecting sex partner | <0.01 | ||||
| No | 345 | 74.8% | 1311 | 48.5% | |
| Yes | 116 | 25.2% | 1390 | 51.5% | |
| Any non-injection use of these drugs in the past 3 months | |||||
| Marijuana | 285 | 62.5% | 1994 | 73.7% | <0.01 |
| Inhalants | 43 | 9.4% | 466 | 17.2% | <0.01 |
| Hallucinogens | 79 | 17.3% | 739 | 27.3% | <0.01 |
| PCP | 48 | 10.5% | 359 | 13.3% | 0.01 |
| Tranquilizers/barbituates | 107 | 23.5% | 1265 | 46.7% | <0.01 |
| Street methadone | 89 | 19.5% | 791 | 29.2% | <0.01 |
| Crack cocaine | 192 | 42.1% | 1636 | 60.5% | <0.01 |
| Methamphetamines | 92 | 20.2% | 880 | 32.5% | <0.01 |
| Heroin | 338 | 74.1% | 2031 | 75.1% | NS |
| Cocaine | 188 | 41.2% | 1536 | 56.8% | <0.01 |
| Other | 51 | 11.2% | 607 | 22.4% | <0.01 |
| Depression – bothered by symptoms: | <0.01 | ||||
| Not at all | 142 | 31.9% | 567 | 21.3% | |
| A little bit | 168 | 37.8% | 985 | 37.0% | |
| Moderately | 81 | 18.2% | 676 | 25.4% | |
| Quite a bit | 43 | 9.7% | 344 | 12.9% | |
| Extremely | 11 | 2.5% | 88 | 3.3% | |
| Anxiety – bothered by symptoms: | <0.01 | ||||
| Not at all | 168 | 37.8% | 637 | 23.9% | |
| A little bit | 160 | 36.0% | 1153 | 43.3% | |
| Moderately | 83 | 18.7% | 601 | 22.6% | |
| Quite a bit | 25 | 5.6% | 216 | 8.1% | |
| Extremely | 9 | 2.0% | 54 | 2.0% | |
| Hostility – bothered by symptoms: | <0.01 | ||||
| Not at all | 189 | 42.4% | 704 | 26.4% | |
| A little bit | 161 | 36.1% | 1144 | 42.9% | |
| Moderately | 61 | 13.7% | 549 | 20.6% | |
| Quite a bit | 24 | 5.4% | 216 | 8.1% | |
| Extremely | 11 | 2.5% | 56 | 2.1% | |
| Self-esteem | <0.01 | ||||
| 1 Lower self-esteem | 1 | 0.2% | 17 | 0.6% | |
| 2 | 85 | 19.4% | 779 | 29.7% | |
| 3 | 294 | 67.1% | 1587 | 60.4% | |
| 4 Higher self-esteem | 58 | 13.2% | 243 | 9.3% | |
| Friends inject w/ used needles | <0.01 | ||||
| None of them, or none inject | 228 | 52.2% | 720 | 27.6% | |
| Fewer than half | 118 | 27.0% | 904 | 34.7% | |
| About half | 42 | 9.6% | 421 | 16.2% | |
| More than half | 30 | 6.9% | 376 | 14.4% | |
| All of them | 19 | 4.3% | 184 | 7.1% | |
| Friends inject w/ used paraphernalia | <0.01 | ||||
| None of them | 175 | 39.1% | 390 | 14.6% | |
| Fewer than half | 113 | 25.2% | 683 | 25.5% | |
| About half | 57 | 12.7% | 565 | 21.1% | |
| More than half | 51 | 11.4% | 638 | 23.8% | |
| All of them | 52 | 11.6% | 402 | 15.0% | |
| General HIV/HCV knowledge | <0.01 | ||||
| <75% correct | 156 | 33.4% | 700 | 25.6% | |
| ≥75% correct | 311 | 66.6% | 2032 | 74.4% | |
| HIV/HCV risk knowledge | <0.01 | ||||
| <75% correct | 336 | 71.9% | 1624 | 59.4% | |
| ≥75% correct | 131 | 28.1% | 1108 | 40.6% | |
| Anti-HIV status | NS | ||||
| Negative | 438 | 96.5% | 2598 | 97.3% | |
| Positive | 16 | 3.5% | 71 | 2.7% | |
| Anti-HCV status | 0.02 | ||||
| Negative | 318 | 69.9% | 1722 | 64.5% | |
| Positive | 137 | 30.1% | 949 | 35.5% | |
| Anti-HBc | NS | ||||
| Negative | 106 | 23.5% | 583 | 22.1% | |
| Positive | 346 | 76.5% | 2060 | 77.9% | |
Collaborative Injection Drug User Study III/Drug User Intervention Trial Study
Exposure to HIV or HBV was not related to injecting alone (prevalence of anti-HIV was 3% and anti-HBc was 77% in those who injected alone vs. 3% and 78%, respectively, in other IDUs). However, anti-HCV prevalence was lower among IDUs who injected alone (30%) than in those who reported injecting with others (35%, p < .05).
Participants who reported always injecting alone in the previous three months reported less frequent or severe occurrence of symptoms of depression, anxiety or hostility toward others. In particular, a higher proportion reported not experiencing these symptoms at all. Subjects who injected with others reported lower self-esteem, and that many or all of their friends inject with syringes or other injection paraphernalia previously used by another IDU. However, those who injected with others also scored higher in terms of general knowledge of HIV and HCV, such as natural history and treatment options, and routes of HIV and HCV transmission.
In multivariate analysis, participants who were black or Hispanic, or older (i.e., age 26–30 years) were more likely to report always injecting alone in the past three months (Table 3). History of drug treatment or incarceration, daily injection, injection with black tar heroin, having an IDU sex partner, being homeless and having completed high school were inversely related to injecting alone.
Table 3.
Multivariate analysis of factors associated with always injecting alone, CIDUS III/DUIT Study1
| AOR2 | 95% Confidence Interval | |
|---|---|---|
| Age | ||
| 15–19 | 1.0 | |
| 20–24 | 1.5 | (0.97–2.3) |
| 25–30 | 1.9 | (1.2–2.9) |
| Race/ethnicity | ||
| White | 1.0 | |
| Hispanic | 1.6 | (1.2–2.1) |
| Black | 1.9 | (1.3–2.9) |
| Other | 1.0 | (0.7–1.5) |
| Homeless | ||
| Yes | 1.0 | |
| No | 0.6 | (0.4–0.8) |
| Education | ||
| HS grad/GED | 1.0 | |
| ≤ 11th grade | 0.7 | (0.5–0.9) |
| Ever in jail | ||
| Yes | 1.0 | |
| No | 0.7 | (0.6–0.97) |
| Ever in drug treatment | ||
| Yes | 1.0 | |
| No | 0.7 | (0.5–0.8) |
| Injects daily or more often | ||
| Yes | 1.0 | |
| No | 0.6 | (0.5–0.8) |
| Have a sexual partner who also injects | ||
| Yes | 1.0 | |
| No | 0.4 | (0.3–0.5) |
Collaborative Injection Drug User Study III/Drug User Intervention Trial Study
Adjusted odds ratio
3.2 Association between injecting alone and HIV/HCV-related risk behavior
IDUs who reported always injecting alone in the past three months were only 15% as likely to inject with a syringe used by another injector (95% confidence interval (CI) 0.11 – 0.19; Table 4). Similarly, as compared to those who injected with others, they were substantially less likely to report using a drug cooker, filtration cotton or rinse water previously used by another IDU (OR=0.14; 95% CI 0.12 – 0.18). To adjust for characteristics that could conceivably confound the association between “always injected alone in the past three months” and recent risk behavior, age, race, homelessness, injection frequency and history of drug treatment or needle exchange use were included in both of the multivariate logistic regression models. The adjusted odds ratio (AOR) for the association between injecting alone and injection with a syringe previously used by another IDU was 0.16 (95% CI 0.12 – 0.21). The model estimating the association between injecting alone and use of cooker, cotton, or rinse water used by another IDUs was adjusted for injection of black tar heroin in addition to all of the other confounding variables; after adjustment for these factors, the AOR was 0.16 (95% CI 0.13 – 0.21).
Table 4.
Association between always injecting alone (past 3 months) and injection risk behavior, CIDUS III/DUIT Study1
| Injected with used syringes | Used cookers, cotton or rinse water previously used by another IDU | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Yes | No | OR | 95% CI | AOR* | 95% CI | Yes | No | OR | 95% CI | AOR* | 95% CI | |||||
| Injected alone | ||||||||||||||||
| Yes | 85 | 18.3% | 379 | 81.7% | 0.15 | (0.11–0.19) | 0.16 | (0.1–0.2) | 193 | 41.6% | 271 | 58.4% | 0.14 | (0.12–0.18) | 0.17 | (0.13–0.2) |
| No | 1627 | 60.6% | 1058 | 39.4% | 1.0 | 1.0 | 2255 | 83.3% | 452 | 16.7% | 1.0 | 1.0 | ||||
Adjusted odds ratios were obtained from a multivariate model that adjusted for age, race/ethnicity, homelessness, history of drug treatment or needle exchange use, daily injection, and injection of black tar heroin.
Collaborative Injection Drug User Study III/Drug User Intervention Trial Study
4. Discussion
In this large multi-center study conducted in five US cities, one out of seven young adult injectors consistently injected alone during the past 3 months. This subgroup of IDUs differed from other young IDUs in several respects; they tended to be somewhat older, less frequent injectors who avoided settings associated with drug use and public injection settings. Fewer IDUs who injected alone had friends who inject drugs or shared injection equipment, and fewer had a sex partner who injects drugs. This subgroup was also more likely to be black or Hispanic, was less likely to have been arrested and had lower HCV prevalence than other IDUs. Differences in injection risk behavior were substantial, as they were only about 15% as likely as other participants to report using a syringe or other injection equipment used by another IDU. However, IDUs injecting alone had lesser HIV and HCV knowledge and they were less likely to attend needle exchange programs or drug abuse treatment programs than other IDUs.
These findings may be relevant to the control of HCV transmission. Recent reports of HCV incidence among young IDUs range between 10 and 40 per 100 person years (Judd et al., 2005; Des Jarlais et al., 2003; Hahn et al., 2002). Thus far, there is no clear and consistent evidence that interventions shown to reduce HIV transmission in IDUs also prevent HCV – this includes studies of needle exchange, drug treatment, disinfectant bleach and HCV education and screening (Crofts et al., 1997; Hagan et al., 1995; Hagan et al., 1999; Kapadia et al., 2004; Rezza et al., 1996; Ompad et al., 2002). The prevalence of unsafe injection in the subgroup of IDUs who inject alone was relatively low – only 18% reported receptive syringe sharing, although 42% reported shared use of other paraphernalia (Table 4). In other studies of young IDUs, recent receptive syringe sharing was reported by 43% in San Francisco (Evans et al., 2003), 49% in Chicago (Thorpe et al., 2002), 30% in New York City (Diaz et al., 2001), 48% in London (Hunter et al., 2000), and 38% in Baltimore (Novelli et al., 2004). Use of cookers, cottons, and rinse water previously used by another IDU was reported among 80% of young IDUs in San Francisco (Evans et al., 2003), 75% in London (Hunter et al., 2000), and 69% in Chicago (Thorpe et al., 2002). In addition, anti-HCV prevalence was significantly lower among IDUs who injected alone, although the difference in prevalence was not substantial – 30% vs. 35% in other IDUs. It may be that the “risk environment” as described by Rhodes and colleagues (2004) is subject to greater personal control when no one else is injecting nearby, although it is unclear whether this practice could prevent HCV transmission.
Injecting alone may confer both protection and risk. Benefits to keeping injecting drug use hidden may include avoiding social and legal problems and reduced risk of acquiring blood borne infections. However, risks may include less frequent contact with other IDUs that could reduce opportunities to learn about drug-related health, risk and protective factors, and may also include increased probability of fatal overdose. In a review of 333 accidental overdose deaths in San Francisco, 32% of deceased patients were found in a room locked from the inside (Davidson et al., 2003). Comparison of the San Francisco death review data to the CIDUS/DUIT sample ignores underlying differences and potential confounding, and inferences may only be drawn with appropriate caution. However, the fact that IDUs injecting alone represented only 15% of our participants as compared to 32% of overdose deaths in San Francisco indicates that injecting alone confers serious risks.
This study has several strengths, including a relatively large sample that yielded a sizable subset of IDUs who had been injecting alone. The use of A-CASI to collect behavioral data and the specificity of the wording in the questionnaire related both to injecting alone and the use of potentially contaminated syringes and other equipment may have decreased measurement error. However, the cross-sectional nature of the study limits our ability to establish a temporal, causal relationship between injecting alone and risk behavior, acquisition of infections or drug overdose. In hindsight, we would have liked to have asked our participants why they chose to inject alone, as we cannot know whether it was a conscious and systematic method to avoid peer pressure and control the injection setting or to avoid others’ knowing that they inject. An early qualitative study showed that many long-term injectors took pains to conceal their drug use, and to distance themselves from users with more chaotic lifestyles (Courtwright et al., 1989). Previous experience of overdose and awareness of overdose risk in these individuals also merits further study.
Achieving personal control over the injection setting and the materials used to prepare and inject drugs appears to be a significant challenge for IDUs and has hampered efforts to prevent HCV transmission. Injection risk behavior among young IDUs who injected alone in this study were remarkably low. However, safety concerns related to overdose risk preclude recommending this as an infection control strategy. Whether this represents “intravention” – a methodical prevention activity generated by a community at risk (Friedman et al., 2004) – cannot be determined from this study, but these IDUs may have useful ideas to contribute to the development of safe injection practices.
Acknowledgments
This study was funded in its entirety by a cooperative agreement from the Centers for Disease Control and Prevention: U64/CCU317662; U64/CCU517656; U64/CCU917655; U64 CCU217659; and U64/CCU071615.
The DUIT Study Team includes the following people: Steffanie Strathdee, Elizabeth Golub, Marie Bailey-Kloch, Karen Yen-Hobelman (Baltimore); Lawrence Ouellet, Susan Bailey, Joyce Fitzgerald (Chicago); Sharon Hudson, Peter Kerndt, Karla Wagner (Los Angeles); Mary Latka, Farzana Kapadia, David Vlahov (New York); Holly Hagan, Hanne Thiede, Nadine Snyder, Jennifer V. Campbell (Seattle); Richard Garfein, David Purcell, Ian Williams, Paige Ingram, Andrea Swartzendruber (CDC).
The authors also acknowledge the following people for their contributions to this research: Yvette Bowser, Peter O’Driscoll, Janet Reeves, Marcella Sapun (Baltimore); Angus Atkins-Trimnell, Mary Bonilla, David Cosey, Jaime Delgado, Julio Garcia, Michelle Giles, Erin Kubalanza, Michael Phillips, Edward Snulligan (Chicago); Marrisa Axelrod, Elizabeth Faber, Lawrence Fernandez Jr., Christian Geannette, Roberto Rojas (Los Angeles); Ebele Benjamin, Sebastian Bonner, Micaela Coady, Joanna Cruz, Sandra DelVecchio, Dirk Jackson, Gregory Malave, Joan Monserrate, Danielle Ompad, Clarisse Miller O’Shea, Yingfeng Wu, Manny Yonko (New York); Stanley Brown, Rong Lee, Susan Nelson, Jef St. De Lore, Carrie Shriver, Jeanette Frazier, Jean Pass, Paul Swenson (Seattle); Yuko Mizuno, Janet Moore, Ann O’Leary, Vincent Raimondi, Scott Santibanez, Roberto Valverde (CDC); Wendi Kuhnert, Himal Dhotre, Leigh Farrington, (CDC Division of Viral Hepatitis); Suzette Bartley, Dollene Hemmerlein (CDC Serum Bank Branch).
The findings and conclusions in this report are those of the author(s) and do not necessarily represent the views of the Centers for Disease Control and Prevention.
Footnotes
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