Multivariate Generalized Estimating Equations Analysis Research Articles

The association between residential eviction and syringe sharing among a prospective cohort of street-involved youth

BackgroundSyringe sharing is a high-risk practice associated with the transmission of infectious diseases, such as HIV and HCV. While youth who contend with housing instability are known to be more likely to engage in high-risk substance use, the potential relationship between being evicted from housing and syringe sharing has not been examined. This study assessed whether residential eviction was associated with syringe sharing among street-involved youth in Vancouver, Canada.MethodsData were derived from the At-Risk Youth Study (ARYS), a prospective cohort of street-involved youth who use drugs age 14–26 in Vancouver, Canada. The study period was June 2007 to May 2014, and the potential relationship between residential eviction and syringe sharing was analyzed using multivariable generalized estimating equations (GEE) logistic regression.ResultsAmong 405 street-involved youth who injected drugs, 149 (36.8%) reported syringe sharing, defined as borrowing or lending a syringe, at some point during the study period. In a multivariable GEE analysis, recent residential eviction remained independently associated with syringe sharing (adjusted odds ratio (AOR) = 1.72, 95% confidence interval (CI): 1.16–2.57), after adjusting for potential confounders.ConclusionsSyringe sharing was significantly elevated among youth who had recently been evicted from housing. These findings indicate that policy and programmatic interventions that increase housing stability may help mitigate high-risk substance use practices among vulnerable youth.

Predictive factors influencing pregnancy rates after intrauterine insemination with frozen donor semen: a prospective cohort study

The extent to which certain parameters can influence pregnancy rates after intrauterine insemination with frozen donor semen was examined prospectively. Between July 2011 and September 2015, 402 women received 1264 IUI cycles with frozen donor semen in a tertiary referral infertility centre. A case report form was used to collect data prospectively. The primary outcome measure was clinical pregnancy rate (CPR), confirmed by detection of a gestational sac and fetal heartbeat using ultrasonography at 7–8 weeks of gestation. Statistical analysis was carried out using generalized estimating equations (GEE) to account for the correlation between observations from the same patient. Overall, CPR per cycle was 17.2%. Multivariate GEE analysis revealed the following parameters as predictive for a successful pregnancy outcome: female age (P = 0.0003), non-smoking or smoking fewer than 15 cigarettes a day (P = 0.0470 and P = 0.0235, respectively), secondary infertility (P = 0.0062), low progesterone levels at day zero of the cycle (P = 0.0164) and use of ovarian stimulation with HMG and recombinant FSH compared with clomiphene citrate and natural cycle (P = 0.0006 and P = 0.0004, respectively). These parameters were the most important factors influencing the success rate in a sperm donation programme.

Predictive value of different covariates influencing pregnancy rate following intrauterine insemination with homologous semen: a prospective cohort study

The aim was to examine the value of different covariates in the prediction of intrauterine insemination (IUI) success. Between July 2011 and September 2015, data from 1401 IUI cycles with homologous semen in 556 couples were collected prospectively, by questionnaire, in a tertiary referral infertility centre. Statistical analysis was performed using generalized estimating equations (GEEs). GEEs were used instead of an ordinary logistic regression model to take into account the correlation between observations from the same person. The primary outcome parameter was clinical pregnancy rate (CPR), confirmed with a gestational sac and fetal heartbeat on ultrasonography at 7–8 weeks. An overall CPR of 9.5% per cycle was observed. Univariate statistical analysis revealed female and male age, male smoking, female body mass index, ovarian stimulation and inseminating motile count (IMC) as covariates significantly influencing CPR per cycle. Multivariate GEE analysis revealed that the only valuable prognostic covariates included female age, male smoking and infertility status (i.e. primary/secondary infertility). IMC showed a significant curvilinear relationship, with first an increase and then a decrease in pregnancy rate.

Hazardous Alcohol Use Associated with Increased Sexual Risk Behaviors Among People Who Inject Drugs.

Alcohol is associated with a multitude of severe health consequences. While risk behaviors related to illicit drug use are commonly studied among people who inject drugs (PWID), the role of alcohol use has received substantially less attention in this population. We explored whether drug and sexual risk behaviors as well as experiences of violence were associated with hazardous alcohol use in a cohort of PWID. Analyses were conducted using observational data from a prospective cohort of community-recruited HIV-negative PWID in Vancouver, Canada. We used the U.S. National Institute on Alcohol Abuse and Alcoholism definition of hazardous alcohol use (i.e., >14drinks/wk or >4 drinks on 1 occasion for men, and >7drinks/wk or >3 drinks on 1 occasion for women). We used multivariable generalized estimating equations (GEE) to identify the factors associated with hazardous alcohol use. Between 2006 and 2012, 1,114 HIV-negative individuals were recruited, and 186 (16.7%) reported hazardous alcohol use in the previous 6months at baseline. In multivariable GEE analyses, having multiple sex partners (adjusted odds ratio [AOR]=1.25), history of sexually transmitted infection (AOR=1.50), experiencing violence (AOR=1.36), and incarceration (AOR=1.29) were each independently associated with hazardous alcohol use. Caucasian ethnicity (AOR=0.56), ≥ daily heroin injection (AOR=0.81), and engagement in addiction treatment (AOR=0.84) were negatively associated with hazardous alcohol use (all p<0.05). A considerable proportion of PWID reported hazardous alcohol use, which was independently associated with reporting sexual, but not drug-related, HIV risk behaviors and experiencing recent violence. Findings suggest a need to integrate regular screening and evidence-based alcohol interventions into treatment efforts for PWID.

Unsafe sexual behaviour associated with hazardous alcohol use among street-involved youth

ABSTRACTWhile risky sexual behaviours related to illicit drug use among street youth have been explored, the impacts of alcohol use have received less attention. This longitudinal study examined hazardous alcohol use among a population of street-involved youth, with particular attention to sexual and drug-related risk behaviours. Data were derived from the At-Risk Youth Study, a prospective cohort of street-involved youth in Vancouver, Canada. The outcome of interest was hazardous alcohol use defined by the US National Institute on Alcohol Abuse and Alcoholism. We used generalized estimating equations (GEEs) analyses to identify factors associated with hazardous alcohol use. Between 2005 and 2014, 1149 drug-using youth were recruited and 629 (55%) reported hazardous alcohol use in the previous 6 months during study follow-up. In multivariable GEE analyses, unprotected sex (adjusted odds ratio [AOR] = 1.28, 95% confidence interval [95% CI] = 1.12–1.46) and homelessness (AOR = 1.35, 95% CI = 1.19–1.54) were independently associated with hazardous alcohol use (all p < .001). Older age (AOR = 0.95, 95% CI = 0.92–0.99), Caucasian ethnicity (AOR = 0.74, 95% CI = 0.61–0.90), daily heroin use (AOR = 0.53, 95% CI = 0.42–0.67), daily crack cocaine smoking (AOR = 0.73, 95% CI = 0.59–0.91), and daily crystal methamphetamine use (AOR = 0.52, 95% CI = 0.42–0.64) were negatively associated with hazardous alcohol use (all p < .05). In sub-analysis, consistent dose–response patterns were observed between levels of alcohol use and unprotected sex, homelessness, and daily heroin injection. In sum, hazardous alcohol use was positively associated with unsafe sexual behaviour and negatively associated with high-intensity drug use. Interventions to address hazardous alcohol use should be central to HIV prevention efforts for street-involved youth.

Psychosocial factors in adherence to antiretroviral therapy among HIV-positive people who use drugs.

Suboptimal adherence to antiretroviral therapy (ART) among HIV-infected people who use illicit drugs (PWUD) remains a significant concern, and there is a lack of effective adherence interventions for this population. Therefore, we sought to identify psychosocial determinants of optimal adherence, including adherence self-efficacy and outcome expectancies, with the aim of informing interventions designed to improve adherence among PWUD. From December 2005 to November 2013, we collected data from the AIDS Care Cohort to evaluate Exposure to Survival Services (ACCESS), a prospective cohort of PWUD in Vancouver, Canada. We used multivariable generalized estimating equations (GEE) analysis to identify longitudinal factors independently associated with 95% or greater adherence to ART. Among 667 participants, including 220 (33%) women, 391 (59%) had 95% or greater ART adherence at baseline. In multivariable GEE analysis, adherence self-efficacy, adjusted odds ratio (AOR) = 1.16, 95% confidence interval (CI) [1.11, 1.21] per 10-point increase, was independently and positively associated with adherence, while negative outcome expectancy, AOR = 0.95, 95% CI [0.93, 0.98], was negatively associated. In light of the ongoing challenges associated with ART adherence among HIV-positive PWUD, and our findings of associations between adherence, self-efficacy, and outcomes expectancies, tailored intervention strategies based on constructs of social learning theory should be implemented and evaluated to improve adherence among HIV-infected PWUD.

Neuromyelitis optica: Evaluation of 871 attacks and 1,153 treatment courses.

Neuromyelitis optica (NMO) attacks often are severe, are difficult to treat, and leave residual deficits. Here, we analyzed the frequency, sequence, and efficacy of therapies used for NMO attacks. A retrospective review was made of patient records to assess demographic/diagnostic data, attack characteristics, therapies, and the short-term remission status (complete remission [CR], partial remission [PR], no remission [NR]). Inclusion criteria were NMO according to Wingerchuk's 2006 criteria or aquaporin-4 antibody-positive NMO spectrum disorder (NMOSD). Remission status was analyzed with generalized estimating equations (GEEs), a patient-based statistical approach. A total of 871 attacks in 185 patients (142 NMO/43 NMOSD, 82% female) were analyzed. The 1,153 treatment courses comprised high-dose intravenous steroids (HD-S; n = 810), plasma exchange (PE; n = 192), immunoadsorption (IA; n = 38), other (n = 80), and unknown (n = 33) therapies. The first treatment course led to CR in 19.1%, PR in 64.5%, and NR in 16.4% of attacks. Second, third, fourth, and fifth treatment courses were given in 28.2%, 7.1%, 1.4%, and 0.5% of attacks, respectively. This escalation of attack therapy significantly improved outcome (p < 0.001, Bowker test). Remission rates were higher for isolated optic neuritis versus isolated myelitis (p < 0.001), and for unilateral versus bilateral optic neuritis (p = 0.020). Isolated myelitis responded better to PE/IA than to HD-S as first treatment course (p = 0.037). Predictors of CR in multivariate GEE analysis were age (odds ratio [OR] = 0.97, p = 0.011), presence of myelitis (OR = 0.38, p = 0.002), CR from previous attack (OR = 6.85, p < 0.001), and first-line PE/IA versus HD-S (OR = 4.38, p = 0.006). Particularly myelitis and bilateral optic neuritis have poor remission rates. Escalation of attack therapy improves outcome. PE/IA may increase recovery in isolated myelitis.

Barriers to Cervical Screening Among Sex Workers in Vancouver.

We longitudinally examined the social, structural, and geographic correlates of cervical screening among sex workers in Metropolitan Vancouver, British Columbia, to determine the roles that physical and social geography play in routine reproductive health care access. Analysis drew on (2010-2013) data from an open prospective cohort of sex workers (An Evaluation of Sex Workers' Health Access). We used multivariable logistic regression with generalized estimating equations (GEE) to model correlates of regular cervical screening. At baseline, 236 (38.6%) of 611 sex workers in our sample had received cervical screening, and 63 (10.3%) were HIV-seropositive. In multivariable GEE analysis, HIV-seropositivity (adjusted odds ratio [AOR] = 1.65; 95% confidence interval [CI] = 1.06, 2.58) and accessing outreach services (AOR = 1.35; 95% CI = 1.09, 1.66) were correlated with regular cervical screening. Experiencing barriers to health care access (e.g., poor treatment by health care staff, limited hours of operation, and language barriers) reduced odds of regular Papanicolaou testing (AOR = 0.81; 95% CI = 0.65, 1.00). Sex workers in Metropolitan Vancouver had suboptimal levels of cervical screening. Innovative mobile outreach service delivery models offering cervical screening as one component of sex worker-targeted comprehensive sexual and reproductive health services may hold promise.

A population-based analysis of use and outcomes of laparoscopic bariatric surgery across socioeconomic groups in Taiwan.

BackgroundWith the growing development of minimally invasive techniques for the treatment of morbid obesity, laparoscopic bariatric surgery (LBS) is increasingly performed. This study aimed to assess the association between patients’ socioeconomic status (SES) and the likelihood of undergoing LBS and related outcomes in Taiwan.MethodsThis nationwide population-based study was conducted by using data from Taiwan’s National Health Insurance Research Database. A total of 3678 morbidly obese patients aged 18 years and older who underwent conventional open bariatric surgery or LBS were identified between 2004 and 2011. Regression analyses were performed using generalized estimating equation (GEE) models to account for the nesting of patients within physician to assess patients’ SES category associated with the use of LBS and related outcomes. Odds ratios (ORs) and 95 % confidence intervals (CIs) were estimated.ResultsCompared with those with medium and low SES (84.6 % and 80.2 %), patients with high SES (88.1 %) had the highest percentage of undergoing LBS (P < 0.001). After adjusting for patient demographics, institution and surgeon characteristics, the multivariate GEE analysis revealed that the highest likelihood of undergoing LBS was noted in morbidly obese patients with high SES (OR = 1.45, 95 % CI 1.10–1.90), followed by those with medium SES (OR = 1.27, 95 % CI 1.04–1.56). In addition, patients with high SES had slightly lower length of hospital stay (LOS; OR = 0.90, 95 % CI 0.82–0.99) and hospital treatment cost (OR = 0.93, 95 % CI 0.87–0.99) than their counterparts after adjustment.ConclusionsThe increased likelihood of undergoing LBS and lower LOS and hospital treatment cost were noted among morbidly obese patients with higher SES. This finding suggests there is the need to improve clinical practice and reduce health disparities in the surgical treatment of morbidly obese patients.

Patterns of, and Factors Associated With, Illicit Pharmaceutical Opioid Analgesic Use in a Prospective Cohort of People Who Inject Drugs in Melbourne, Australia

Background: People who inject drugs (PWID) are a key population engaging in pharmaceutical opioid analgesic (PO) use, yet little is known about patterns of illicit PO use among this group. Objectives: The aims of this research were to measure the prevalence and frequency of lifetime and past-month illicit PO use and injection in a sample of regular PWID, to examine patterns of past-month illicit PO use within individuals over time, and to identify factors independently associated with past-month illicit PO use. Methods: Data were drawn from a prospective cohort study of regular PWID (N = 666) in Melbourne, Australia. Data from five waves of annual data collection (including baseline) were analyzed descriptively and using generalized estimating equations (GEE). Results: At baseline, 59% of participants reported lifetime illicit PO use and 20% reported past-month use, predominantly through injecting. Most illicit PO users at baseline transitioned to nonuse of illicit POs across the study period. In multivariable GEE analysis, factors associated with past-month illicit PO use included past-year arrest [adjusted odds ratio (AOR): 1.39], opioids other than heroin as drug of choice (AOR: 5.14), experiencing poorer physical health (AOR: 0.98) and a range of other drug use variables. Conclusions: We found little evidence of ongoing illicit PO use among those followed up, with illicit PO use linked to polydrug use more broadly. Nonetheless, trends in illicit PO use among PWID should continue to be monitored and harm reduction interventions implemented to reduce the associated public health risks.

Drug use patterns associated with risk of non-adherence to antiretroviral therapy among HIV-positive illicit drug users in a Canadian setting: a longitudinal analysis.

BackgroundAmong people living with HIV/AIDS, illicit drug use is a risk for sub-optimal treatment outcomes. However, few studies have examined the relative contributions of different patterns of drug use on adherence to antiretroviral therapy (ART). We sought to estimate the effect of different types of illicit drug use on adherence in a setting of universal free HIV/AIDS treatment and care.MethodsUsing data from ongoing prospective cohorts of HIV-positive illicit drug users linked to comprehensive pharmacy dispensation records in Vancouver, Canada, we examined factors associated with ≥95% prescription refill adherence using generalized estimating equations (GEE) logistic regression.ResultsBetween 1996 and 2013, 692 ART-exposed individuals were followed for a median of 42.7 months (Interquartile Range: 29.1–71.7). In multivariable GEE analyses, heroin injection (Adjusted Odds Ratio [AOR] = 0.75, 95% Confidence Interval [CI]: 0.66–0.85) as well as cocaine injection (AOR = 0.80, 95% CI: 0.72–0.90) were associated with lower likelihoods of optimal adherence. Methadone maintenance therapy (AOR = 1.88, 95% CI: 1.68–2.11) was associated with a greater likelihood of adherence.ConclusionsPeriods of heroin and cocaine injection appeared to have the most deleterious impact upon antiretroviral adherence. The findings point to the need for improved access to treatment for heroin use disorder, particularly methadone, and highlight the need to identify strategies to support ART adherence among cocaine injectors.

A Novel Approach to a Retrospective Longitudinal Analysis of Dose Change or Discontinuation of Imatinib Therapy in Chronic Phase–Chronic Myeloid Leukemia

▪Imatinib (IM) is a cornerstone in the treatment of chronic myeloid leukemia (CML). Dose change or discontinuation of IM in patients who experience sustained molecular response is a subject of debate.We retrospectively studied 142 CML patients in chronic phase (Table 1) treated with IM and followed-up during 2000-2013 at our institution. Dose changes, discontinuation of therapy, cytogenetic and molecular analyses were regularly recorded during follow-up. Patients’ history was subdivided into 483 treatment time-periods at constant dosage. Response was evaluated at the end of each treatment period. We assessed whether the probability of observing a complete cytogenetic response (CCyR) or a molecular response (MR: complete, CMR or major, MMR) or a progression were influenced by treatment dose and/or duration.We applied generalized estimating equation (GEE) logistic models for the analysis of longitudinal panel data. These models are designed to account for individual patient variation due to repeated measurements during each patient’s follow-up.Out of 483 time periods at constant IM dose, 236 were followed by dose modification, 116 by IM discontinuation, 29 by a change to other treatments due to tolerability issues or non-response; 102 were still ongoing without dose changes.Treatment response: 74% of time periods resulted in a CCyR and 2.3% showed no response; 31.9% showed a CMR, 29.6% showed a MMR (MR3, MR4, MR4.5), 35.6% a suboptimal response, 2.9% no MR. CMR+MMR was observed in 61.5% time periods.Periods at standard dose showed a higher response rate, both when considering CCyR (response rate after low, standard, high dose: 69.3%, 79.6%, 68%, respectively, P=0.023) and when considering MR (CMR after low, standard, high dose: 27%, 40.5%, 15.4%, respectively, P<0.001; CMR + MMR after low, standard, high dose: 53.4%, 69.8%, 52.3%, respectively, P=0.001).After adjusting for length of treatment period in a multivariate GEE model, dose lost significance and treatment duration was the only significant predictor of CCyR (P<0.001).In a GEE analysis of MR accounting for treatment duration, reduction in CMR rate after periods at high dose compared with periods at standard dose remained significant (P=0.025). Treatment dose lost significance when considering CMR+MMR.In 32 patients who discontinued IM therapy for >1 mos and then re-started IM, the CR rate after a period preceded by a treatment suspension was significantly higher than in other periods (CCyR: 85.7% vs. 73%, P=0.058; CMR 55.1% vs. 29.3%, P=0.001). In a GEE model with dose category, duration of treatment and previous suspension as covariates, both duration and previous suspension maintained a positive significant association to CCyR (P<0.001, P=0.034, respectively), to CMR (both P<0.001) and to CMR+MMR (P<0.001, P=0.006, respectively).Cytogenetic progression rate at the end of a period of IM treatment was 7.1% while molecular progression rate was 12.8%.Treatment dose was not associated to progression: cytogenetic progression after low, standard, high dose: 6.1%, 6.7%, 10.5%, respectively, P=0.428; molecular progression after low, standard, high dose: 14.8%, 11.3%, 13%, respectively, P=0.584. In a multivariate GEE analysis, neither dose nor duration of treatment predicted progression. After adding type of previous treatment (IM, other drug, no treatment) as a covariate, treatment periods preceded by at least 1 month of discontinuation had a significantly lower molecular progression rate (P=0.011).The possibility of varying dosage is often considered in “real-life” patient clinical management. In our study, 62% of time periods were followed by a dose change, but this did not affect response and progression rate after accounting for length of treatment period. The prompt response to resumed IM therapy suggests that patients may be candidates for intermittent therapy.Future studies could use the same statistical model to pick up individual patient variation in longitudinal data collected over time, including trials at reduced IM dose or of “on-off” therapy or on new TKI.Table 1Patients’ characteristicVariableDescriptionN. of patients142Sex M/F58%/42%Age at diagnosis (years), median (range)52 (18-78)N. of IM treatment periods483IM dosage, N (%)Low dose (100-300 mg/day)163 (34%)Standard dose (400 mg/day)242 (50%)High dose (450-800 mg/day)78 (16%)Duration of IM at constant dosage (days), median (range)258 (7-4526) DisclosuresNo relevant conflicts of interest to declare.

The clearance of oral high-risk human papillomavirus infection is impaired by long-term persistence of cervical human papillomavirus infection

Persistence of high-risk (HR-) human papillomavirus (HPV) infection of the uterine cervix increases the risk of cervical cancer. Oral HPV infections are among potential covariates of long-term genotype-specific persistent cervical HR-HPV infections. It is not known whether this persistence reflects inability of the host to reject HPV infections in general. A case–control setting was designed to estimate the covariates of long-term persistent cervical HR-HPV infections using multivariate generalized estimating equation (GEE) models. HPV was detected with PCR using GP05+/GP06+-primers and genotyped for 24 HPVs with a Multimetrix-kit. The cases (n = 43) included women who had genotype-specific persistent cervical HR-HPV infection for at least 24 months (24M+) and controls were women who tested repeatedly HPV-negative in their cervical samples (n = 52). These women represent a sub-cohort of the Finnish Family HPV Study. The cases differed significantly from the HPV-negative controls in several aspects: they were younger, had a longer mean time to incident oral HPV infection (40.7 versus 23.6 months), longer duration of oral HPV persistence (38.4 versus 14.1 months), and longer time to clearance of their oral HPV infection (50.0 versus 28.2 months). In multivariate GEE analysis, the second pregnancy during the follow up was the only independent predictor with significant protective effect against 24M+ persistent cervical HR-HPV infections, OR of 0.15 (95% CI 0.07–0.34). To conclude, long-term persistent cervical HR-HPV infections are associated with a prolonged clearance of oral HR-HPV infections while new pregnancy protects against persistent cervical HR-HPV infections.

Prevalence and correlates of nonmedical prescription opioid use among a cohort of sex workers in Vancouver, Canada

BackgroundThe nonmedical use of prescription opioids (POs) is a major public health concern, causing extensive morbidity and mortality in North America. Canada has the second highest consumption rate of POs globally and data indicate nonmedical PO use (NPOU) is growing among key populations and increasingly available in street-level drug markets. Despite accumulating evidence documenting the rise of NPOU, few studies have systematically examined NPOU in Canada among key vulnerable populations, such as sex workers. This study prospectively evaluated the prevalence and correlates of NPOU within a Vancouver cohort of sex workers over three-years follow-up. MethodsData were drawn from an open prospective cohort, AESHA (An Evaluation of Sex Workers Health Access) in Metro Vancouver, Canada (2010–2013). Women were recruited through outreach from outdoor street locations and indoor venues. Bivariate and multivariable logistic regression using Generalized Estimating Equations (GEE) were used to examine social and structural correlates of NPOU over 36 months. ResultsOf the 692 sex workers at baseline, close to one-fifth (n=130, 18.8%) reported NPOU (injection or non-injection) in the last six months. In multivariable GEE analyses, factors independently correlated with recent NPOU were: exchanging sex while high (AOR 3.26, 95%CI 2.29–4.64), police harassment/arrest (AOR 1.83, 95%CI 1.43–2.35), intimate partner injects drugs (AOR 1.66, 95%CI 1.11–2.49), and recent physical/sexual intimate partner violence (AOR 1.65, 95%CI 1.21–2.24). ConclusionOur results demonstrate that nearly one-fifth of sex workers in Metro Vancouver report NPOU. Factors independently statistically associated with NPOU included exchanging sex while high, police harassment/arrest, a drug injecting intimate partner and recent physical/sexual intimate partner violence. The high prevalence of NPOU use among sex workers underscores the need for further prevention and management strategies tailored to this key population. The correlates of NPOU uncovered here suggest that structural interventions may be further implemented to ameliorate this growing concern.

High prevalence and partner correlates of physical and sexual violence by intimate partners among street and off-street sex workers.

ObjectivesIntimate partner violence (IPV) is associated with increased risk of HIV among women globally. There is limited evidence and understanding about IPV and potential HIV risk pathways among sex workers (SWs). This study aims to longitudinally evaluate prevalence and correlates of IPV among street and off-street SWs over two-years follow-up.MethodsLongitudinal data were drawn from an open prospective cohort, AESHA (An Evaluation of Sex Workers Health Access) in Metro Vancouver, Canada (2010–2012). Prevalence of physical and sexual IPV was measured using the WHO standardized IPV scale (version 9.9). Bivariate and multivariable logistic regression using Generalized Estimating Equations (GEE) were used to examine interpersonal and structural correlates of IPV over two years.ResultsAt baseline, 387 SWs had a male, intimate sexual partner and were eligible for this analysis. One-fifth (n = 83, 21.5%) experienced recent physical/sexual IPV at baseline and 26.2% over two-years follow-up. In multivariable GEE analysis, factors independently correlated with physical/sexual IPV in the last six months include: childhood (<18 years) sexual/physical abuse (adjusted odds ratio [AOR] = 2.05, 95% confidence interval [CI]: 1.14–3.69), inconsistent condom use for vaginal and/or anal sex with intimate partner (AOR = 1.84, 95% CI: 1.07–3.16), <daily prescription opioid use (AOR = 1.72, 95% CI: 1.02–2.89), providing financial support to intimate partner (AOR = 1.65, 95% CI: 1.05–2.59), and sourcing drugs from intimate partner (AOR = 1.62, 95% CI: 1.02–2.26).DiscussionOur results demonstrate that over one-fifth of SWs in Vancouver report physical/sexual IPV in the last six months. The socio-structural correlates of IPV uncovered here highlight potential HIV risk pathways through SWs’ intimate, non-commercial partner relationships. The high prevalence of IPV among SWs is a critical public health concern and underscores the need for integrated violence and HIV prevention and intervention strategies tailored to this key population.

Sex-for-Crack exchanges: associations with risky sexual and drug use niches in an urban Canadian city

BackgroundWhile crack cocaine has been associated with elevated sexual risks and transmission of HIV/STIs, particularly in the context of street-based sex work, few empirical studies have examined correlates of direct sex-for-crack exchanges. This study longitudinally examined the correlates of sex-for-crack exchanges and associated effects on sexual risk outcomes among street-based female sex workers (SW) who use drugs in Vancouver, Canada.MethodsData were drawn from a prospective cohort of street-based SWs (2006–2008), restricted to those who smoke crack cocaine. Multivariable generalized estimating equations (GEE) were employed to examine the correlates of exchanging sex for crack. A confounding model using GEE quasi-Poisson regression modeled the independent effect of exchanging sex for crack on number of clients/week.ResultsOf 206 SWs, 101 (49%) reported sex-for-crack exchanges over 18 months of follow-up. In multivariable GEE analyses, sharing a crack pipe with a client (aOR = 1.98; 95%CI: 1.27-3.08) and smoking crack in a group of strangers (e.g., in an alley or crackhouse) (aOR = 1.70; 95% CI: 1.13-2.58) were independently correlated with sex-for-crack exchanges. In our confounding model, exchanging sex for crack (aIRR = 1.34; 95% CI: 1.07-1.69) remained significantly associated with servicing a greater number (>10) of clients/week.ConclusionsThese findings reveal elevated sexual- and drug- risk patterns among those who exchange sex for crack. The physical and social environment featured prominently in our results as a driver of sex-for-crack exchanges, highlighting the need for gender-sensitive multilevel approaches to harm reduction, STI and HIV prevention that address SWs’ environment, individual level factors, and the interplay between them.

Incarceration among street-involved youth in a Canadian study: Implications for health and policy interventions

BackgroundRisk factors for incarceration have been well described among adult drug using populations; however, less is known about incarceration among at-risk youth. This study examines the prevalence and correlates of incarceration among street-involved youth in a Canadian setting. MethodsFrom September 2005 to May 2012, data were collected from the At-Risk Youth Study, a prospective cohort of street-involved youth aged 14–26 who use illicit drugs. Generalized estimating equation (GEE) logistic regression was used to identify factors associated with recent incarceration defined as incarceration in the previous six months. ResultsAmong 1019 participants, 362 (36%) reported having been recently incarcerated during the study period. In multivariate GEE analysis, homelessness (adjusted odds ratio [AOR]=1.60), daily crystal methamphetamine use (AOR=1.56), public injecting (AOR=1.33), drug dealing (AOR=1.48) and being a victim of violence (AOR=1.68) were independently associated with incarceration (all p<0.05). Conversely, female gender (AOR=0.48), lesbian, gay, bisexual, transgender or two-spirited (LGBTT) identification (AOR=0.47) and increasing age of first hard drug use (AOR=0.96) were negatively associated with incarceration (all p<0.05). ConclusionIncarceration was common among our study sample. Youth who were homeless, used crystal methamphetamine, and engaged in risky behaviors including public injection and drug dealing were significantly more likely to have been recently incarcerated. Structural interventions including expanding addiction treatment and supportive housing for at-risk youth may help reduce criminal justice involvement among this population and associated health, social and fiscal costs.

Patterns of injection drug use cessation during an expansion of syringe exchange services in a Canadian setting

BackgroundNeedle and syringe programmes (NSPs) have been shown to reduce HIV risk among people who inject drugs (IDUs). However, concerns remain that NSPs delay injecting cessation. MethodsIndividuals reporting injection drug use in the past six months in the greater Vancouver area were enrolled in the Vancouver Injection Drug Users Study (VIDUS). Annual estimates of the proportion of IDU reporting injecting cessation were generated. Generalized estimating equation (GEE) analysis was used to assess factors associated with injecting cessation during a period of NSP expansion. ResultsBetween May 1996 and December 2010, the number of NSP sites in Vancouver increased from 1 to 29 (P<0.001). The estimated proportion of participants (n=2710) reporting cessation increased from 2.4% (95% confidence interval [CI]: 0.0–7.0%) in 1996 to 47.9% (95% CI: 46.8–48.9%) in 2010 (P<0.001). In a multivariate GEE analysis, the authors observed an association between increasing calendar year and increased likelihood of injecting cessation (Adjusted Odds Ratio=1.17, 95% CI: 1.15, 1.19, P<0.001). ConclusionThe proportion of IDU reporting injecting cessation increased during a period of NSP expansion, implying that increased NSP availability did not delay injection cessation. These results should help inform community decisions on whether to implement NSPs.

Police confrontations among street-involved youth in a Canadian setting

BackgroundStreet-level policing has been recognized as a driver of health-related harms among people who inject drugs (IDU). However, the extent of interaction between police and street-involved youth has not been well characterized. We examined the incidence and risk factors for police confrontations among street-involved youth in a Canadian setting. MethodsUsing data derived from participants enrolled in the At-Risk Youth Study (ARYS) between 2005 and 2011, we assessed factors associated with being stopped, searched, or detained by police without arrest in the previous six months using generalized estimating equations (GEE) with logit link for binary outcomes. ResultsAmong 991 participants followed during the study period, 440 (44.4%) reported being stopped, searched, or detained by police for an incidence density of 49.20 (95% confidence interval [CI]: 36.42–65.01) per 100 person years. In multivariate GEE analyses, factors associated with police confrontations included: male gender (adjusted odds ratio [AOR]=1.35), homelessness (AOR=2.05), recent incarceration (AOR=1.78), daily cannabis use (AOR=1.31), daily heroin injecting (AOR=1.36), crack pipe/syringe sharing (AOR=1.61), injection drug use (AOR=1.37), public drug use (AOR=2.19), sex work involvement (AOR=1.67), and drug dealing (AOR=1.49) (all p<0.05). In total, 19.0% of participants reported that police confiscated their drug paraphernalia without arresting them. Additionally, 16.9% of individuals reported experiencing violence at the hands of police. ConclusionWe found that various factors, such as homelessness and markers of more severe addiction, increased the likelihood of being confronted by police, and police confrontations were associated with markers of health-related harm among street youth. These findings highlight the need for social and structural interventions that best enable police to fulfil public safety and public order objectives without negatively influencing health behaviours of street youth.

Severe food insecurity is associated with elevated unprotected sex among HIV-seropositive injection drug users independent of HAART use

Despite emerging evidence of a significant adverse relationship between food insecurity and sexual risk-taking, data have been primarily derived from resource-constrained settings and HIV-negative populations. To our knowledge, this study is the first to longitudinally evaluate the relationship between food insecurity and unprotected sex among HIV-seropositive people who inject drugs [injection drug users (IDUs)] both on and not on HAART. Longitudinal analyses were restricted to HIV-positive IDUs who completed baseline and at least one follow-up visit in a prospective cohort (AIDS Care Cohort to evaluate Exposure to Survival Services, 2005-2009). We constructed a multivariate logistic model using generalized estimating equations (GEEs) to assess an independent relationship between severe food insecurity (e.g., hunger due to lack of access or means to acquire food) and unprotected vaginal/anal sex. Among 470 HIV-positive IDUs, the median age was 42 years (interquartile range 36-47) with 61% men and 39% women. The prevalence of severe food insecurity was 71%, with no differences by HAART use. Severe food insecure IDUs were marginally less likely to have a suppressed HIV-1 RNA viral load (31 vs. 39%, P = 0.099). In multivariate GEE analyses, severe food insecurity [adjusted odds ratio = 2.68, 95% confidence interval 1.49-4.82] remained independently correlated with unprotected sex among HIV-positive IDUs, controlling for age, sex/gender, married/cohabitating partner, binge drug use, homelessness, and HAART use. These findings highlight a crucial need for structural HIV interventions that incorporate targeted food assistance strategies for IDUs. Given recent evidence of poor virological response among food insecure individuals on HAART, innovative HIV care models should integrate targeted food security programs and early access to HAART.