Using geographic information systems to assess spatial patterns of drug use, selection bias and attrition among a sample of injection drug users

Spatial and Environmental Correlates of Prevalence of Treatment for Substance Use Disorders, Retention, and SUD Services Utilization in South Sardinia

This study explored the economic, social, and spatial correlates of treatment prevalence, retention, and service utilization for substance use disorder (SUD) in South Sardinia. Data from 1,667 patients with an ICD-10 diagnosis of SUD were extracted from the medical records of individuals assisted by three public addiction services in 2019. We used a spatial autoregressive model, a parametric proportional hazard model, and Poisson regression to examine the associations of spatial factors and residents' socioeconomic status with the prevalence of treatment at the census block level, treatment retention, and SUD service utilization at the individual level. The prevalence was higher among residents of areas closer to competent treatment centers, with the worst building conservation status, a lower percentage of high school and university graduates, and a higher percentage of unemployed, divorced, separated, or widowed residents. Men who were older at the time of their first treatment access; primary users of cocaine, cannabis, and alcohol; had higher education level; and who lived far from competent treatment centers and closer to drug trafficking centers interrupted their treatment earlier. Primary heroin users experienced more SUD treatment encounters. Living in economically and socially disadvantaged areas and near treatment facilities was associated with a higher prevalence, whereas living near drug-dealing centers and far from competent treatment centers was associated with a decrease in treatment retention.

Open data and injuries in urban areas-A spatial analytical framework of Toronto using machine learning and spatial regressions

Injuries have become devastating and often under-recognized public health concerns. In Canada, injuries are the leading cause of potential years of life lost before the age of 65. The geographical patterns of injury, however, are evident both over space and time, suggesting the possibility of spatial optimization of policies at the neighborhood scale to mitigate injury risk, foster prevention, and control within metropolitan regions. In this paper, Canada’s National Ambulatory Care Reporting System is used to assess unintentional and intentional injuries for Toronto between 2004 and 2010, exploring the spatial relations of injury throughout the city, together with Wellbeing Toronto data. Corroborating with these findings, spatial autocorrelations at global and local levels are performed for the reported over 1.7 million injuries. The sub-categorization for Toronto’s neighborhood further distills the most vulnerable communities throughout the city, registering a robust spatial profile throughout. Individual neighborhoods pave the need for distinct policy profiles for injury prevention. This brings one of the main novelties of this contribution. A comparison of the three regression models is carried out. The findings suggest that the performance of spatial regression models is significantly stronger, showing evidence that spatial regressions should be used for injury research. Wellbeing Toronto data performs reasonably well in assessing unintentional injuries, morbidity, and falls. Less so to understand the dynamics of intentional injuries. The results enable a framework to allow tailor-made injury prevention initiatives at the neighborhood level as a vital source for planning and participatory decision making in the medical field in developed cities such as Toronto.

Neighborhood Alcohol Environment: Differential Effects on Hazardous Drinking and Mental Health by Sex in Persons Living with HIV (PLWH)

Despite greater mental health co-morbidities and heavier alcohol use among PLWH, few studies have examined the role of the neighborhood alcohol environment on either alcohol consumption or mental health. Utilizing cross-sectional data from a cohort study in a southern U.S. metropolitan area, we examine the association between neighborhood alcohol environments on hazardous drinking and mental health among 358 in-care PLWH (84% African American, 31% female). Multilevel models were utilized to quantify associations between neighborhood alcohol exposure on hazardous drinking and effect modification by sex. Neighborhood alcohol density was associated with hazardous drinking among men but not women. Women living in alcohol dense neighborhoods were nearly two-fold likely to report depression compared to those in less dense neighborhoods, with no association between neighborhood alcohol density and depression among men. Neighborhood alcohol environments may be an important contextual factor to consider in reducing heavy alcohol consumption and improving mental health among PLWH.

Examining the Social Context of Injection Drug Use: Social Proximity to Persons Who Inject Drugs Versus Geographic Proximity to Persons Who Inject Drugs

In this analysis, we used social network and spatial data to examine associations between people's drug injection status and their social and/or spatial proximity to others who injected drugs. We recruited 503 rural Kentucky residents who used drugs to participate in the Social Networks among Appalachian People (SNAP) Study (2008-2010). Interviewer-administered surveys collected information on recent (past 6 months) sex, drug-use, and social-support network members (n = 897 ties). Using network simulations, we determined a threshold for the association between social proximity to others who injected drugs and recent injection status ("socially proximal" was defined by a shortest path ≤2). We defined "geographically proximal" as the median road-network distance between pairs of individuals who both injected drugs (≤7 miles (≤11.2 km)). Logistic regression was used to determine the independent and joint associations between the number of socially and/or geographically proximal injecting peers and a person's injection status. After adjustment, the odds of recent injection increased by 0.4% for each injecting peer who was geographically proximal but not socially proximal, 12% for each geographically and socially proximal injecting peer, and 22% for each injecting peer who was socially proximal but not geographically proximal. When implementing network-based interventions which promote cessation of injection drug use, investigators should consider collecting sociometric network data to examine whether the intervention diffuses through the network and whether there are additive or threshold effects.

Geographical Information System Evaluation and Trends of Nonaccidental Trauma at a Level I Trauma Center, Pilot Study

PREMISE

Although trauma may be considered a random act, geographical patterns of trauma potentially emerge. Our institution is unique in that it rests at an intersection of two of the highest areas of poverty and assault in New York City and has adequate data to analyze these patterns.

METHODS

We review the incident reports logged by emergency medical services (EMS) technicians arriving with intentionally injured trauma patients from January 1 to December 31, 2013 at a single institution. After acquisition of this data, it was placed into a computer file using an individual identifying numbers for each incident along with latitude and longitude coordinates determined by global positioning software for each event. The data were separated into blunt and penetrating categories. Penetrating trauma was further separated into the type of instrument used: edged weapon or firearm. Kernel density estimate using the Crimestat program was then performed to determine the epicenters with the highest incidents of nonaccidental trauma.

RESULTS

Two hundred eighty-three patients were evaluated for assault-related trauma. Two hundred fifty-four patients were included in the mapping of the data with almost equal blunt and penetrating trauma. Seventy-four percent of trauma occurred from 6 PM to 6 AM, and 41% occurring between midnight and 6 AM. Of patients, 32.7% were found to be assaulted at their home address. Regression analysis demonstrated that each type of trauma had unique epicenters of likelihood for occurrence.

CONCLUSIONS

We can only speculate the reasons for many of these results at this time and further research into the sociological, psychological, and environmental factors is required. A high proportion of patients are assaulted at their home addresses. Further study is necessary to improve patient care with additional data provided by emergency medical services, police departments and surrounding hospitals.

Triangulating Syndemic Services and Drug Treatment Policy: Improving Drug Treatment Portal Locations in Baltimore City

THE PROBLEM

The prevalence of injection drug use (IDU) and incidence of human immunodeficiency virus (HIV) remain high in Baltimore, where IDU is a primary HIV risk factor. Substance use disorders and HIV are related syndemically--their causes and consequences interact synergistically. Baltimore is increasingly considering the syndemic relationship of substance use disorders, IDU, and HIV in making decisions about drug treatment funding and location.

PURPOSE OF ARTICLE

Our goal was to empirically identify the optimal location of new drug treatment programs through the development and application of a novel, practical tool.

KEY POINTS

Syndemic triangles were constructed to measure and visualize unmet need for drug treatment services. These data were used to determine priority zones for new treatment centers.

CONCLUSIONS

The application of this tool helped inform strategies for locating drug treatment services in Baltimore, and its successful use suggests its potential value in other metropolitan areas.

Modeling the impact of place on individual methadone treatment outcomes in a national longitudinal cohort study

BACKGROUND

Little has been published on the effect of geography on methadone treatment outcomes.

OBJECTIVE

To measure the effect of place on longitudinal outcomes Methods: From 2003 to 2006, 215 clients were recruited to a cohort study of methadone treatment. Participants had their address and clinic geocoded. Treatment outcomes were measured at intake, at one and three years posttreatment using the Maudsley Addiction Profile instrument. Spider diagrams and buffer rings were used to visually map clinics and clients. Regression models were used to measure the effect of place.

RESULTS

Client's accommodation and social and criminal problems in the region had a medium to large effect on heroin use. Analysis of buffer rings revealed that clients located within a 10-km radius of a major clinic demonstrated poorer outcomes in terms of heroin use. Conclusion/Importance: Findings illustrated the relevance of geography on drug treatment outcomes and the planning of services.

Comparison of geographic methods to assess travel patterns of persons diagnosed with HIV in Philadelphia: how close is close enough?

Travel distance to medical care has been assessed using a variety of geographic methods. Network analyses are less common, but may generate more accurate estimates of travel costs. We compared straight-line distances and driving distance, as well as average drive time and travel time on a public transit network for 1789 persons diagnosed with HIV between 2010 and 2012 to identify differences overall, and by distinct geographic areas of Philadelphia. Paired t-tests were used to assess differences across methods, and analysis of variance was used to assess between-group differences. Driving distances were significantly longer than straight-line distances (p<0.001) and transit times were significantly longer than driving times (p<0.001). Persons living in the northeast section of the city traveled greater distances, and at greater cost of time and effort, than persons in all other areas of the city (p<0.001). Persons living in the northwest section of the city traveled farther and longer than all other areas except the northeast (p<0.0001). Network analyses that include public transit will likely produce a more realistic estimate of the travel costs, and may improve models to predict medical care outcomes.

Spatial accessibility of drug treatment facilities and the effects on locus of control, drug use, and service use among heroin-injecting Mexican American men

BACKGROUND

This study explores the spatial accessibility of outpatient drug treatment facilities and the potential relationship with drug use-related outcomes among Mexican American heroin users.

METHODS

Secondary data on 219 current and former heroin-injecting Mexican American men aged 45 and older were drawn from a research study in Houston, Texas. We used geographic information systems (GIS) to derive two spatial accessibility measures: distance from one's place of residence to the closest drug treatment facility (in minutes); and the number of facilities within a 10-minute driving distance from one's place of residence. Exploratory logistic regression analyses examined the association between the spatial accessibility of drug treatment facilities and several drug use-related outcomes: internal locus of control (LOC); perceived chances and worries of injecting in the next six months; treatment utilization; and location of last heroin purchase.

RESULTS

Participants with greater spatial access to treatment programs were more likely to report a higher chance of injecting in the near future. However, while current heroin users were more worried about injecting in the next six months, greater spatial access to treatment programs seemed to have a buffering effect. Finally, those who lived closer to a treatment programs were more likely to have last purchased heroin inside the neighborhood versus outside the neighborhood. Spatial accessibility was not associated with internal LOC or treatment utilization.

CONCLUSION

The findings showed that the presence of outpatient treatment facilities-particularly services in Spanish-may influence perceived risk of future heroin use and purchasing behaviors among Mexican American men. Implications for future spatially-informed drug use research and the planning of culturally and linguistically responsive drug treatment programs are discussed.

Intraurban mobility and its potential impact on the spread of blood-borne infections among drug injectors in Tijuana, Mexico

We explored intraurban mobility of Tijuana, Mexico, injection drug users (IDUs). In 2005, 222 IDUs underwent behavioral surveys and infectious disease testing. Participants resided in 58 neighborhoods, but regularly injected in 30. From logistic regression, "mobile" IDUs (injecting ≥3 km from their residence) were more likely to cross the Mexico/U.S. border, share needles, and get arrested for carrying syringes-but less likely to identify hepatitis as an injection risk. Mobile participants lived in neighborhoods with less drug activity, treatment centers, or migrants, but higher marriage and home ownership rates. Mobile IDUs should be targeted for outreach and further investigation. The study's limitations are noted.

Using spatial analysis to demonstrate the heterogeneity of the cardiovascular drug-prescribing pattern in Taiwan

BACKGROUND

Geographic Information Systems (GIS) combined with spatial analytical methods could be helpful in examining patterns of drug use. Little attention has been paid to geographic variation of cardiovascular prescription use in Taiwan. The main objective was to use local spatial association statistics to test whether or not the cardiovascular medication-prescribing pattern is homogenous across 352 townships in Taiwan.

METHODS

The statistical methods used were the global measures of Moran's I and Local Indicators of Spatial Association (LISA). While Moran's I provides information on the overall spatial distribution of the data, LISA provides information on types of spatial association at the local level. LISA statistics can also be used to identify influential locations in spatial association analysis. The major classes of prescription cardiovascular drugs were taken from Taiwan's National Health Insurance Research Database (NHIRD), which has a coverage rate of over 97%. The dosage of each prescription was converted into defined daily doses to measure the consumption of each class of drugs. Data were analyzed with ArcGIS and GeoDa at the township level.

RESULTS

The LISA statistics showed an unusual use of cardiovascular medications in the southern townships with high local variation. Patterns of drug use also showed more low-low spatial clusters (cold spots) than high-high spatial clusters (hot spots), and those low-low associations were clustered in the rural areas.

CONCLUSIONS

The cardiovascular drug prescribing patterns were heterogeneous across Taiwan. In particular, a clear pattern of north-south disparity exists. Such spatial clustering helps prioritize the target areas that require better education concerning drug use.

A GIS-based methodology for improving needle exchange service delivery

BACKGROUND

A variety of legal, social and logistical factors can prevent individuals from accessing formal needle exchange programmes. One common solution to this problem is satellite exchange, which involves collaborating with people who already use an exchange to deliver needles and other supplies to those unable to access the exchange. While this approach can be very successful, one potential problem is that those most willing to deliver needles to their peers are often members of social networks that are already well connected with the needle exchange, leading to duplication of effort. In this paper we describe a simple and novel method for identifying groups of people who are demonstrably in need of improved access to needles, and for re-targeting efforts to meet the needs of those people. The method described was piloted at the Homeless Youth Alliance, San Francisco, USA, and further refined at Clean Needles Now, Los Angeles, USA.

METHODS

People accessing needle exchange sites were asked to participate in a survey with two questions: "where were you and what time was it last time someone borrowed a needle from you?" and "where were you and what time was it last time you had to borrow a needle from someone else?" Responses were geocoded, and maps produced showing 'hotspots' where people were frequently finding themselves without needles.

RESULTS

Satellite needle exchange was refined from an ad-hoc activity into one which focused on delivering needles to those with empirically demonstrable need. Maps produced in the process also proved valuable in discussions with local officials and other agencies about funding, as well as needle provision policy and practices.

CONCLUSION

We describe a method for rapidly assessing, describing, and responding to unmet and under-met need among injecting drug users. The method is particularly well-suited to organizations with extremely limited resources.

Bayesian hierarchical spatial modeling of substance abuse patterns following a mass trauma: the role of time and place

To illustrate how spatial modeling methods may provide insight about the relation between proximity to mass trauma and substance use, we examined the role of proximity to a terrorist event in determining risk of substance use related diagnoses. Previous analyses that have assessed changes in substance use following mass traumas such as terrorist attacks have produced conflicting results. We used Bayesian hierarchical modeling methods to assess whether distance from the World Trade Center (WTC) site in the aftermath of the September 11, 2001 terrorist attacks was associated with risk of substance use related diagnoses. In analyses controlling for age, gender, median household income, and employment-related exposure to the terrorist attacks, we found that each two mile increment in distance away from the WTC site was associated with 18% more substance use related diagnoses in the population we studied; this relation between distance from the WTC and substance use related disorder was the opposite of the relations observed one year before the same attacks in the same area. By accounting for spatial relationships that may influence the population risk of substance use health disorder, this approach helps explain some of the conflicting observations in the extant literature. These methods hold promise for the characterization of disease risk where spatial patterning of exposures and outcomes may matter.

Mapping violence and policing as an environmental-structural barrier to health service and syringe availability among substance-using women in street-level sex work

BACKGROUND

Within street-based sex work and substance-using populations, there is growing evidence to support the role of place, both physical setting and social meanings attached to place, in mediating the effectiveness and reach of health and harm reduction services.

METHODS

Social mapping was used to explore how health service and syringe availability may be impacted at the geographic level by avoidance of physical settings due to violence and policing among women in street-level sex work. Through a community-based research partnership and extensive peer-led outreach over a 6-month period, women were invited to participate in interview-questionnaires and mapping of their community, working conditions, and access to resources. Results were compiled used ArcGIS software and GIS street maps. In secondary analysis, logistic regression was used to model the geographic association (using likelihood ratio and significance at p<0.05) and stratified models were run to assess differential patterns of avoidance based on age, ethnicity and drug use.

RESULTS

The findings reveal a significant geographic relationship between a heavily concentrated core area of health and syringe availability and avoidance of physical settings due to violence and policing by 198 women in street-level sex work in Vancouver, Canada. Of particular concern, this correlation is significantly elevated among younger and Aboriginal women, active injection drug users, and daily crack cocaine smokers, suggesting significant environmental-structural barriers to interventions among these vulnerable populations.

CONCLUSIONS

The resultant displacement of sex work to primarily industrial settings and side streets pushes women further from health and social supports and reduces access to safer injection and drug use paraphernalia. This study offers important evidence for environmental-structural level prevention and safer environment interventions, supported by legal reforms, that facilitate safer sex work environments, including spatial programming, peer-based prevention, outreach and mobile resources, and peer-supervised safer sex work settings.

Spatial distribution of HIV prevalence and incidence among injection drugs users in St Petersburg: implications for HIV transmission

INTRODUCTION

The HIV/AIDS epidemic in St Petersburg, as in much of Russia, is concentrated among injection drug users (IDU) in whom prevalence reached 30% in 2003. Understanding the dynamics of the epidemic is important in developing appropriate responses in the resource-constrained context of Russian cities such as St Petersburg.

METHODS

IDU were contacted and screened to create a seronegative cohort for prevention and vaccine studies. At screening, individuals provided sociodemographic, drug use, and injection and sex-related risk behavior data. Seronegative individuals who enrolled in the cohort were followed for one year and tested for HIV semiannually. Residential addresses were entered into a geographical information system programme and analysed for spatial clustering using Moran's I and nearest-neighbor analysis.

RESULTS

We mapped 788 of the 900 study participants to discrete locations within St Petersburg; 236 (29.9%) were HIV seropositive at baseline. Although there was no clustering of the study population as a whole, HIV-infected individuals were tightly clustered and prevalence co-clustered with high frequency of heroin injection, receptive syringe sharing, being younger than 24 years, and living with parents. These clusters were restricted to 5% of populated areas of the city. We mapped 18 of 20 incident cases detected among the cohort, and more than half were located within or adjacent to the clusters.

INTERPRETATION

Spatial analysis identified linkages between disease prevalence and risky injection behaviors that were not evident using traditional epidemiological analysis. The analysis also identified where resources might be allocated geographically for maximum impact in slowing the HIV epidemic among IDU.

Mapping the prevalence of problem gambling and its association with treatment accessibility and proximity to gambling venues

This study examined geographic variation in the prevalence of problem gambling in Ontario and the association with various demographic factors and proximity to treatment for problem gambling and gambling venues. Drawing upon multiple sources, secondary data analysis was undertaken based on multivariate statistical methods and techniques of geographic information systems (GIS). Regional variation in prevalence of problem gambling was found in the province. P revalence of problem gambling was associated with many demographic characteristics, as well as mental disorders, co-occurring substance abuse problems, and physical health status. Geographic access to treatment was not associated with the risk of being a problem gambler. However, proximity to gambling venues was marginally important in predicting risk of problem gambling. Results are interpreted in the context of needs-based planning of treatment and prevention programs for problem gambling.

Geomatics in injury prevention: the science, the potential and the limitations

BACKGROUND

Geomatics describes the activities involved in acquiring and managing geographical data and producing geographical information for scientific, administrative and technical endeavors. As an emerging science, geomatics has a great potential to support public health. Geomatics provides a conceptual foundation for the development of geographic information systems (GIS), computerized tools that manage and display geographical data for analytical applications. As descriptive epidemiology typically involves the examination of person, place and time in the occurrence of disease or injury, geomatics and GIS can play an important role in understanding and preventing injury.

AIM

This article provides a background to geomatics for those in the injury prevention field who are unfamiliar with spatial analysis. We hope to stimulate researchers and practitioners to begin to use geomatics to assist in the prevention of injury.

METHODS

The authors illustrate the potential benefits and limitations of geomatics in injury prevention in a non-technical way through the use of maps and analysis.

RESULTS

By analysing the location of patients treated for fall injuries in Central Toronto using GIS, some demographic and land use variables, such as household income, age, and the location of homeless shelters, were identified as explanatory factors for the spatial distribution.

CONCLUSION

By supporting novel approaches to injury prevention, geomatics has a great potential for efforts to combat the burden of injury. Despite some limitations, those with an interest in injury prevention could benefit from this science.

The effect of individual, program, and neighborhood variables on continuity of treatment among dually diagnosed individuals

This study reviewed the medical charts of 271 patients diagnosed with co-morbid mental health and substance-use disorders who were discharged from a hospital acute inpatient unit to various outpatient treatment programs in Philadelphia. Geographic Information Systems (GIS) technology and logistic regression modeling were employed to investigate the effects of individual, neighborhood, and program-level variables on arrival to the first treatment appointment within 30 days of discharge. Four models are presented. The results of the study suggest that having had three or more treatment episodes prior to inpatient hospitalization, and living in a neighborhood in which temporary or transitional, and presumably, other low income housing is located, increased the likelihood of patients continuing with treatment in the community. Discharge to the preadmission address, a chief complaint of bizarre behavior, close proximity of two or more liquor and/or beer stores, a high density of narcotics anonymous (NA) and/or alcoholics anonymous (AA) meetings within the neighborhood, an axis I diagnosis of substance-induced mood disorder, and a urine drug screen positive for heroin reduced the likelihood of attending outpatient treatment. We conclude that geographic and community variables as they relate to substance abuse may add an important dimension to our understanding of patient functioning and well being in the community following inpatient treatment.

The increase in the association of education and cocaine use over the 1980s and 1990s: evidence for a 'historical period' effect

During the 1980s the social distribution of adult cocaine use in the US changed, according to qualitative analyses, and its use became more prevalent in the lower as compared to the upper social strata. In this paper, we use national data to investigate the association of education and adult cocaine use to test whether this trend represents either a 'historical period' process that occurred concurrently across adults of all age groups or a cohort process that started with younger cohorts and only extended to older age groups as these younger cohorts aged. We also estimate the extent to which the emergence of crack cocaine use accounts for trends in the socioeconomic distribution of cocaine use over historical time. To address these questions we analyze data from each survey of the National Household Survey on Drug Abuse from 1979 to 1998 inclusive. The results point to a "historical period" process that is explained in large part--but not entirely--by the emergence of crack cocaine. Important differences are apparent across racial and ethnic groups, as well as age groups. Cocaine use joins a growing list of potentially addictive drugs that have become more prevalent in the lower as compared to the upper social strata over historical time.

Geostatistics and GIS: tools for characterizing environmental contamination

Geostatistics is a set of statistical techniques used in the analysis of georeferenced data that can be applied to environmental contamination and remediation studies. In this study, the 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE) contamination at a Superfund site in western Maryland is evaluated. Concern about the site and its future clean up has triggered interest within the community because residential development surrounds the area. Spatial statistical methods, of which geostatistics is a subset, are becoming increasingly popular, in part due to the availability of geographic information system (GIS) software in a variety of application packages. In this article, the joint use of ArcGIS software and the R statistical computing environment are demonstrated as an approach for comprehensive geostatistical analyses. The spatial regression method, kriging, is used to provide predictions of DDE levels at unsampled locations both within the site and the surrounding areas where residential development is ongoing.

Making health data maps: a case study of a community/university research collaboration

This paper presents the main findings from a collaborative community/university research project in Canada. The goal of the project was to improve access to community health information, and in so doing, enhance our knowledge of the development of community health information resources and community/university collaboration. The project built on a rich history of community/university collaboration in Southeast Toronto (SETO), and employed an interdisciplinary applied research and action design. Specific project objectives were to: (1) develop via active community/university collaboration a geographic information system (GIS) for ready access to routinely collected health data, and to study logistical, conceptual and technical problems encountered during system development; and (2) to document and analyze issues that can emerge in the process of community/university research collaboration. System development involved iteration through community user assessment of need, development or refinement of the GIS, and assessment of the GIS by community users. Collaborative process assessment entailed analysis of archival material, interviews with investigators and participant observation. Over the course of the project, a system was successfully developed, and favorably assessed by users. System development problems fell into four main areas: maintaining user involvement in system development, understanding and integrating data, bringing disparate data sources together, and making use of assembled data. Major themes emerging from the community/university collaborative research process included separate community and university cultures, time as an important issue for all involved, and the impact of uncertainty and ambiguity on the collaborative process.

Risking risk: the influence of types of capital and social networks on the injection practices of drug users

Although syringe exchange and other harm reduction interventions have generally been effective in reducing bloodborne pathogen incidence among injection drug users (IDUs), in some cases a minority of IDUs continues to engage in risky injection behavior. Building on emerging perspectives in social epidemiology and research on drug use in anthropology that point to the importance of examining fundamental social causes of risk behavior, or what puts individuals at risk for risk, this study used a multilevel perspective to explore whether forms of capital, social network characteristics, and other contextual factors influence continued risky injection behavior. Quantitative and qualitative data were collected on IDUs in the city of Marseilles, France, where sterile injection equipment has been legal and officially promoted since 1995. In multivariate analysis on data concerning active users, location in the densest part of a large, interconnected network of IDUs greatly increased the likelihood of risky injection practices, while there was a non-significant tendency for low Acquired Cultural and Economic Capital to predict this behavior. Among the strongest individual-level characteristics to predict this outcome were illicit use of prescribed medication, generally high dose buprenorphine, and unprotected sex. Parental abuse of psychoactive drugs during the subject's childhood, on the other hand, greatly decreased the chances of engaging in risky injection behavior. Additionally, qualitative data analysis suggests that risky injection may be linked to lack of resources to procure drugs, and not simply to inadequate sterile injection equipment. Further research, including ecological models, is needed to better understand how fundamental social conditions are related to "risk for risk". However, public health interventions can already address the need for community-level interventions, while rethinking the consequences of inaccessible drugs and unintended "leakage" from the introduction of buprenorphine and other medicalized treatments for opiate dependency.

Can individual competence factors prevent adult substance and alcohol abuse in low- and high-income areas?

This study investigates the role of individual competence factors as modifiers of the risk for adult substance and alcohol abuse in relation to living in high- or low-income areas. The study group consisted of 7,577 18-year-old Swedish conscripts followed for substance and alcohol abuse until the age of 45 ears. Records of alcohol and substance abuse were obtained from official registers. In the 25-year follow-up period, 166 (2.2%) persons were identified as substance abusers and 286 (3.8%) as alcohol abusers. Subjects with many (from five to nine) behavioral risk factors and many (from four to five) competence factors had significantly less adult alcohol and substance abuse in low-income areas compared with those who had few competencies. This finding was also true for alcohol abuse in high-income areas. Experimentation with drugs and alcohol use before conscription was the most powerful risk factor for adult alcohol abuse and substance abuse in both income areas. The results of this study indicate that knowledge of competence factors is important in preventing abuse, especially among high-risk persons coming from low-income areas.

Birds of a feather: using a rotational box plot to assess ascertainment bias

BACKGROUND

Comparability of study participants with non-participants is customarily assessed by contrasting the distributions of sociodemographic characteristics. Such comparisons do not necessarily provide insight into whether or not participants of a given subgroup are similar to non-participants of the same subgroup. A geographical information system (GIS) may provide such insight by visually displaying the spatial distributions of participants and non-participants. In a previously reported study of heterosexuals at elevated risk for human immunodeficiency virus (HIV), traditional methods suggested distributional differences in the demographic characteristics of participants and non-participants.

METHODS

Based on residential address co-ordinates for each subgroup member, we used the subgroup's centroid as the origin and constructed a 360 degrees series of overlapping box plots of the distance of subgroups members to the origin, thereby producing closed polygons for each of the box plot demarcators.

RESULTS

These rotational box plots revealed similar geographical distributions for most participant and non-participant subgroups, with the exception of African-American men and women.

CONCLUSIONS

Observed differences resulted in part from the study design, and provided some insight into sampling problems encountered in social network studies. Based on Tobler's supposition that 'nearby things tend to be alike', the rotational box plot is a useful additional tool for investigating sample bias.