Health outcomes associated with crack-cocaine use: Systematic review and meta-analyses

Highlights

• Crack-cocaine use is common but health outcomes are not systematically reviewed.

• Strong associations exist for various infectious diseases, e.g., HIV, hepatitis C.

• Moderate evidence associations exist for neonatal health and violence.

• Primary research is needed to understand the distinct risks and harm pathways.

Abstract

Background

Crack-cocaine use is prevalent largely in socio-economically marginalized populations in the Americas. Its use has been associated with diverse health outcomes, yet no recent or systematic reviews of these exist.

Methods

A systematic review of health outcomes associated with crack-cocaine use was performed, using MEDLINE, Scopus, Web of Science, CINAHL, PsycINFO, and LILACS up to October 2016. Search terms included crack-cocaine and health outcome-related keywords, targeting peer-reviewed studies on quantified health outcomes associated with crack-cocaine use. Random effects meta-analyses produced pooled odds ratios. Levels of evidence for major results were assessed using the GRADE approach. A review protocol was registered with PROSPERO (CRD42016035486).

Results

Of 4700 articles returned, 302 met eligibility criteria, reporting on health outcomes for 14 of 22 ICD-10 chapters. Conclusive evidence and meta-analyses showed positive associations between crack-cocaine use and blood/sexually transmitted diseases (HIV and hepatitis C virus, others); moderate evidence and meta-analyses supported associations with neonatal health, and violence. There were mixed associations for mental and other health outcomes, yet insufficient evidence to perform meta-analyses for many categories (e.g., mortality). Most underlying research was of limited or poor quality, with crack-cocaine commonly assessed as a secondary covariate.

Conclusions

Crack-cocaine use was associated with a range of health outcomes, although it was unclear if there was direct causal impact, interactions between risk factors, or external drivers of both crack-cocaine use and outcomes. Rigorous epidemiological studies are needed to systematically assess health outcomes of crack-cocaine use and underlying pathways, also to inform evidence-based interventions.

Introduction

An estimated 18.3 million persons aged 16–64 used cocaine in 2014, representing 0.3–0.4% of the global population, rendering cocaine one of the most commonly used illicit drugs (United Nations Office on Drugs and Crime, 2016). In 2013, the estimated spread of cocaine-use disorder was 7.4 (95% confidence interval (CI): 7.2–7.5) million cases, representing 1.0 (95% CI: 0.7–1.4) million years lived with disability, globally (Vos et al., 2015). While powder (hydrochloride) cocaine has been used for decades, crack-cocaine emerged as a sub-type in the 1980s (Hatsukami and Fischman, 1996, Inciardi et al., 2006). Crack-cocaine is prepared through heat evaporation of powdered cocaine with a base (often sodium bicarbonate) to produce a more combustible, alkaline cocaine product, which is typically inhaled (‘smoked’) (Gossop et al., 1994).

Crack-cocaine use occurs mostly in young, socio-economically marginalized (e.g., poor, homeless), urban populations, and disproportionately in the Americas (Chaves et al., 2011, Fischer et al., 2013, Fischer et al., 2006, Fischer and Coghlan, 2007, Santos Cruz et al., 2013). Precise user population estimates do not exist. Local data indicate that crack-cocaine use became increasingly prevalent in the Americas from the 1990s forward (Dunn et al., 1996, Edlin et al., 1994, Fischer and Coghlan, 2007, Werb et al., 2010), with up to 50% of street drug users in Canada (Fischer et al., 2006, I-Track, 2013, Werb et al., 2010) and 35% of illicit drug users, or approximately 370,000 persons, in Brazilian state capital cities (Bastos and Bertoni, 2014) reporting crack-cocaine use.

Previous reviews have established that cocaine use is associated with a range of health problems including cognitive impairment (Jovanovski et al., 2005, Potvin et al., 2014), respiratory disease (Filho et al., 2004), cardiovascular disease (Lange and Hillis, 2001), congenital malformations (Rizk et al., 1996), and premature mortality (Degenhardt et al., 2011). In recent years, growing evidence has reported severe morbidity and premature mortality outcomes (e.g., respiratory illness, HIV seroconversion) associated with crack-cocaine use (DeBeck et al., 2009, Haim et al., 1995). Many of these appear distinct from the risks associated with cocaine use, possibly facilitated by crack-cocaine’s distinct pharmacology and routes of administration, or the predominantly marginalized status and distinct behaviors and exposures of users (Fischer et al., 2016, Gossop et al., 1994, Hatsukami and Fischman, 1996, Levine et al., 1991). Few reviews on the health risks associated with crack-cocaine use exist, and those that do are non-systematic, limited in scope, and outdated (Associação Brasileira de Psiquiatria, 2012, Cornish and O'Brien, 1996, Costa et al., 1998, Cruz et al., 2013, Ettinger and Albin, 1989, Haim et al., 1995, Laposata and Mayo, 1993, Smart, 1991).

Given the comparably high prevalence of crack-cocaine use, its multiple, serious associated health outcomes suggested by individual studies, and the absence of current and comprehensive reviews, we decided to conduct a systematic review of health outcomes associated with crack-cocaine use. The objectives of this systematic review were to:

• Provide a comprehensive and systematic review of health outcomes associated with crack-cocaine use and discuss potential pathways of harm.

• Describe the evidence of associations between crack-cocaine use and health outcomes by health category defined per International Statistical Classification of Diseases and Related Health Problems, 10th Revision (ICD-10) (World Health Organization, 2015)

• and perform meta-analyses where possible.