Mortality risk for cocaine abusers in relation to heroin use: a follow-up study

All-cause and cause-specific mortality among people with regular or problematic cocaine use: a systematic review and meta-analysis

AIMS

To estimate pooled all-cause and cause-specific mortality risk for people with regular or problematic cocaine use.

METHODS

Systematic review and meta-analysis of prospective or retrospective cohort studies or clinical trials (n ≥30) of people with regular or problematic cocaine use with data on all-cause or cause-specific mortality. Of 2808 papers, 28 were eligible and reported on 21 cohorts, with a total 170 019 individuals. Cohorts identified based on acute care for drug poisoning or other severe health presentation were excluded. Title/abstract screening was conducted by one reviewer; a second reviewer independently checked 10% of excluded studies. Two reviewers conducted full-text screening. Data were extracted by one reviewer and checked by a second. A customized review-specific study reporting quality/risk of bias tool was used. Data on crude mortality rates (CMR) and standardized mortality ratios were extracted for both all-cause and cause-specific mortality. Standardized mortality ratios were imputed where not provided by the author using extracted data and information from the Global Burden of Disease Study 2017. Data were pooled using a random-effects model.

RESULTS

The pooled all-cause crude mortality rate was 1.24 per 100 person-years [95% confidence interval (CI) = 0.86, 1.78; n = 16 cohorts], but with considerable heterogeneity (I²  = 98.8%). The pooled all-cause standardized mortality ratio (SMR) was 6.13 (95% CI = 4.15, 9.05; n = 16 cohorts). Suicide (SMR = 6.26, 95% CI = 2.84, 13.80), accidental injury (SMR = 6.36, 95% CI = 4.18, 9.68), homicide (SMR = 9.38, 95% CI 3.45-25.48) and AIDS-related mortality (SMR = 23.12, 95% CI = 11.30, 47.31) were all elevated compared with age and sex peers in the general population.

CONCLUSIONS

There are elevated rates of mortality among people with regular or problematic cocaine use for traumatic deaths and deaths attributable to infectious disease.

Injecting Alone is More Common among Men, Frequent Injectors and Polysubstance Users in a Sample of People Who Inject Drugs

Injecting alone increases the risk of a fatal overdose. We examined the extent of such behavior in a sample of people who inject drugs (PWID) and the typical characteristics of those injecting alone at least once during the past four weeks. A cross-sectional study. PWID recruited from the street and from low-threshold services in seven Norwegian cities in September 2017 (n = 359). Associations between characteristics and injecting alone were examined using logistic regression analysis. The independent variables were gender (female/male), age, having received overdose-prevention education (no/yes), and, in the past four weeks; homelessness/shelter use (no/yes), in opioid substitution treatment (no/yes), injecting ≥ four days a week (no/yes), and substances injected (opioids only/opioids and other/other only/central stimulants (CS) only/CS and other/CS and opioids/CS, opioids and other). The adjusted odds ratios (aOR) and 95% Confidence Intervals (CI) were reported. Of the 359 PWID, 84.4% reported having injected alone. Males were more likely than females to inject alone (aOR = 1.88 95% CI 1.00-3.54). Furthermore, those injecting frequently (aOR = 1.99 95% CI 1.02-3.86) and those injecting multiple substances (CS, opioids and other) (aOR = 2.94 95% CI 1.01-8.58) were more likely to inject alone compared to those injecting less frequently and opioids only. Although not statistically significant, the effect sizes in the logistic regression models suggest that polysubstance use may be driven by CS use. Injecting alone was common in our sample of PWID, and male gender, frequent injecting and polysubstance injecting were associated with this behavior.

Differences in mortality in a cohort of cocaine use disorder patients with concurrent alcohol or opiates disorder

AIMS

To study mortality in a cohort of cocaine use disorder patients, and compare results in those with concurrent alcohol or opiates disorder.

DESIGN, SETTING AND PARTICIPANTS

A cohort of 10 539 cocaine use disorder individuals entering drug treatment in public out-patient centres in the city of Barcelona was followed from 1997 to 2011. Participants were divided at baseline into three groups: those with only cocaine use disorder (CUD), those with cocaine and alcohol use disorder but not opioid (CAUD) and those with cocaine and opioid use disorder (COUD). Mortality was assessed through the Spanish National Mortality Register.

MEASUREMENTS

Crude mortality rates (CMR), standardized mortality ratios (SMR) and rate ratios (RR) were calculated for each group. A multivariable Cox regression model was fitted to obtain adjusted mortality hazard ratios (aHR) of CAUD and COUD with respect to CUD. Specific mortality causes were also examined.

FINDINGS

The total of 716 deaths registered resulted in a CMR = 6.0/1000 person-years (PY); 95% confidence interval (CI) = 5.1-7.0 for CUD, CMR = 5.8/1000 PY (95% CI = 4.9-6.7) for CAUD and CMR = 20.7/1000 PY (95% CI = 18.8-22.8) for COUD, with no significant differences among sexes. Compared with the general population, mortality was four times higher (SMR = 4.1, 95% CI = 3.5-4.8) among CUD, more than three times among CAUD (SMR = 3.4, 95% CI = 2.9-3.9) and more than 10 times among COUD (SMR = 11.6, 95% CI = 10.5-12.8), being always higher in women. External injuries, led by overdose, accumulated the biggest percentage of deaths among the three groups, but infectious diseases showed the highest excess mortality. Some differences regarding causes of death were observed between the three groups.

CONCLUSIONS

Mortality risk and excess mortality are significantly greater among those with cocaine and opiates use disorder than among people with only cocaine use disorder or cocaine and alcohol use disorder.

Patterns of substance use and mortality risk in a cohort of 'hard-to-reach' polysubstance users

AIMS

To examine the mortality risk in a cohort of 'hard-to-reach' polysubstance users and its putative associations with substance use. Specifically, we estimated all-cause mortality risk as a function of individual substance use indicators, and then as a function of their complex, 'real-life' patterns as identified through latent class analysis (LCA).

DESIGN

Prospective cohort study among street- and low-threshold service-recruited polysubstance users included between September and November 2013 and followed through the National Cause of Death Registry until 31 October 2015.

SETTING

Seven Norwegian cities.

PARTICIPANTS

A total of 884 users of illegal opioids and/or stimulants. Of these, 357 were in opioid substitution treatment (OST) at the time of inclusion. Forty-four participants died during follow-up.

MEASUREMENTS

Primary outcome: all-cause mortality risk. Unadjusted and adjusted Cox proportional hazard (PH) regression models (covariates: male, age, homelessness/shelter use, overdose experience, OST status, years of injecting, individual substance use indicators, city, use patterns). LCA models estimated separately for those in and those not in OST due to measurement invariance.

FINDINGS

The crude mortality rate was 2.52 per 100 person-years. Standardized mortality ratio was 26.11 [95% confidence interval (CI) = 10.06-54.87] for women and 10.71 (95% CI = 6.39-16.81) for men. No single drug use indicator, such as 'heroin injection' or 'number of drugs used', was associated with the mortality risk. However, meaningful use patterns were identified; three OST and non-OST patterns each. The non-OST patterns 'polysubstance injectors' [hazard ratio (HR) = 3.45, 95% CI = 0.98-12.14] and 'low frequent injectors' (HR = 3.17, CI = 1.05-9.56) were associated significantly with the mortality risk even when adjusted for other known risk factors.

CONCLUSIONS

In a Norwegian prospective cohort study, 'hard-to-reach' polysubstance users had a more than 10 times higher mortality risk than the general population. Mortality risk was not a function of any single drug use indicator, but two distinct combinations of substances, frequencies and routes of administration were associated with the mortality risk.

Similarities and changes between 15- and 24-year survival and retention rates of patients in a large medical-affiliated methadone maintenance treatment (MMT) center

BACKGROUND

Environmental and social trends and patients' characteristics may affect predictors for methadone maintenance treatment (MMT) outcome.

METHODS

We have expanded our previous study of predictors for MMT outcome (from 619 to 890 patients) and the study period (from 15 to 24 years). Survival and retention in MMT since admission to the MMT clinic (6/1993-6/2016) and until death or study closure (6/2017) were compiled and analyzed.

RESULTS

Of 890 patients ever admitted (10,146.9 person-years (py)), 237 passed away (116 while in MMT). The mortality rate did not differ between those who stayed or left (2.6 vs. 2.1 per 100 py, p = 0.1), but it was lower among those who stayed ≥1 year during any admission (2.1 vs. 3.3 per 100 py, respectively, p = 0.004). Age <40 years, no hepatitis C or B, no HIV, and no benzodiazepine abuse after one year predicted longer survival (multivariate analyses). No opiate or benzodiazepine abuse after one year, methadone dose ≥100 mg/d, no DSM-IV-TR Axis II diagnosis only, and no direct hospital referral predicted longer retention. Cocaine abuse predicted poor retention and survival among 271 patients admitted during the extended part of the study period.

CONCLUSIONS

Predictors for retention (associated with MMT outcome) and mortality (associated with pre-treatment comorbidity) after 24 years were similar to those after 15 years. Cocaine abuse as a predictor of both poor retention and poor survival in the later period may reflect the escalating trend for cocaine abuse and should be studied if related to other unmonitored substances.

Morbidity and mortality in homeless individuals, prisoners, sex workers, and individuals with substance use disorders in high-income countries: a systematic review and meta-analysis

BACKGROUND

Inclusion health focuses on people in extremely poor health due to poverty, marginalisation, and multimorbidity. We aimed to review morbidity and mortality data on four overlapping populations who experience considerable social exclusion: homeless populations, individuals with substance use disorders, sex workers, and imprisoned individuals.

METHODS

For this systematic review and meta-analysis, we searched MEDLINE, Embase, and the Cochrane Library for studies published between Jan 1, 2005, and Oct 1, 2015. We included only systematic reviews, meta-analyses, interventional studies, and observational studies that had morbidity and mortality outcomes, were published in English, from high-income countries, and were done in populations with a history of homelessness, imprisonment, sex work, or substance use disorder (excluding cannabis and alcohol use). Studies with only perinatal outcomes and studies of individuals with a specific health condition or those recruited from intensive care or high dependency hospital units were excluded. We screened studies using systematic review software and extracted data from published reports. Primary outcomes were measures of morbidity (prevalence or incidence) and mortality (standardised mortality ratios [SMRs] and mortality rates). Summary estimates were calculated using a random effects model.

FINDINGS

Our search identified 7946 articles, of which 337 studies were included for analysis. All-cause standardised mortality ratios were significantly increased in 91 (99%) of 92 extracted datapoints and were 11·86 (95% CI 10·42-13·30; I2=94·1%) in female individuals and 7·88 (7·03-8·74; I2=99·1%) in men. Summary SMR estimates for the International Classification of Diseases disease categories with two or more included datapoints were highest for deaths due to injury, poisoning, and other external causes, in both men (7·89; 95% CI 6·40-9·37; I2=98·1%) and women (18·72; 13·73-23·71; I2=91·5%). Disease prevalence was consistently raised across the following categories: infections (eg, highest reported was 90% for hepatitis C, 67 [65%] of 103 individuals for hepatitis B, and 133 [51%] of 263 individuals for latent tuberculosis infection), mental health (eg, highest reported was 9 [4%] of 227 individuals for schizophrenia), cardiovascular conditions (eg, highest reported was 32 [13%] of 247 individuals for coronary heart disease), and respiratory conditions (eg, highest reported was 9 [26%] of 35 individuals for asthma).

INTERPRETATION

Our study shows that homeless populations, individuals with substance use disorders, sex workers, and imprisoned individuals experience extreme health inequities across a wide range of health conditions, with the relative effect of exclusion being greater in female individuals than male individuals. The high heterogeneity between studies should be explored further using improved data collection in population subgroups. The extreme health inequity identified demands intensive cross-sectoral policy and service action to prevent exclusion and improve health outcomes in individuals who are already marginalised.

FUNDING

Wellcome Trust, National Institute for Health Research, NHS England, NHS Research Scotland Scottish Senior Clinical Fellowship, Medical Research Council, Chief Scientist Office, and the Central and North West London NHS Trust.

Mortality Trends among Cocaine Users Treated between 1989 and 2013 in Northern Italy: Results of a Longitudinal Study

A total of 852 participants attending 11 centers for addiction treatment in north Italy following problems due to cocaine abuse between 1989 and 2013 were recruited. Two typologies were created: cocaine users (never heroin) (CU) and heroin and cocaine users (HCU). During the 38-year follow-up period, 4.8% of the whole cohort died. Over the whole period, tumors were the main causes of death; starting in 2010, suicide deaths became the first cause of death. Among CUs, most deaths were due to road accidents and suicide; among HCUs, most of the deaths were from opiate overdose and from cardio-circulatory system diseases. The excess mortality observed for all causes in either sex was 6.24; higher in females (15.03) as compared in males (6.23), higher in HCUs (9.06) as compared in CUs (5.21). The directly age-sex standardized mortality rates were 5.31 per 100, higher for females, declining after 2009 for all patients and after 2004 for HCUs. Multivariate analysis confirms the decreasing trend in the risk of death and shows a higher mortality risk for participants in the under-25 age group. Among cocaine users, special attention should be paid to the prevention of suicide deaths.

An exploratory study of information sources and key findings on UK cocaine-related deaths

Cocaine-related deaths have increased since the early 1990s in Europe, including the UK. Being multi-factorial, they are difficult to define, detect and record. The European Monitoring Centre for Drugs and Drug Addiction commissioned research to: describe trends reported to Special Mortality Registries and General Mortality Registers; provide demographic and drug-use characteristic information of cases; and establish how deaths are identified and classified. A questionnaire was developed and piloted amongst all European Monitoring Centre for Drugs and Drug Addiction Focal Point experts/Special Mortality Registries: 19 (63%) responded; nine countries provided aggregated data. UK General Mortality Registers use cause of death and toxicology to identify cocaine-related deaths. Categorisation is based on International Classification of Diseases codes. Special Mortality Registries use toxicology, autopsy, evidence and cause of death. The cocaine metabolites commonly screened for are: benzoylecgonine, ecgonine methyl ester, cocaethylene and ecgonine. The 2000s saw a generally accelerating upward trend in cases, followed by a decline in 2009. The UK recorded 2700-2900 deaths during 1998-2012. UK Special Mortality Registry data (2005-2009) indicate: 25-44 year-olds account for 74% of deaths; mean age=34 (range 15-81) years; 84% male. Cocaine overdoses account for two-thirds of cases; cocaine alone being mentioned/implicated in 23% in the UK. Opioids are involved in most (58%) cocaine overdose cases.

Mortality Risk Among Heroin Abusers: Clients and Non-clients of Public Treatment Centers for Drug Addiction

In Europe, the prevalence of problematic heroin consumption is declining but, in spite of the constant rise in the number of treated patients, many of them do not turn to a public treatment center (PTC) for their drug addiction. The aim of this study is to study the mortality risk separately for heroin abusers PTC clients and non-PTC clients (i.e., those never treated at a PTC).

METHODS

Cohort study on 959 subjects resident in the metropolitan area of Bologna who went to a health service (i.e., hospital, emergency unit) or to a PTC following problems due to heroin abuse for the first time between 01/01/2004 and 31/12/2009. Standardized mortality ratios (SMRs) were calculated, and regression analysis using the Poisson method was used.

RESULTS

Elevated and statistically significant SMRs were found in both genders, irrespective of the contact facility, being higher for PTC clients. Among non-PTC clients 28% of deaths overall were from AIDS or infectious diseases (6% PTC clients), 17% from opiate overdose (6% PTC clients) and 14% from violent causes (6% PTC clients). Multivariate analysis showed a higher mortality risk for patients who used both heroin and cocaine and for concomitant abuse of benzodiazepines.

CONCLUSIONS

The characteristics of patients never before treated for addiction prompts a reflection on the presence of a hidden group of patients who are hard to reach, who have a high mortality risk and who turn to health care treatment facilities only in the event of an emergency.

Gender differences in mortality and risk factors in a 13-year cohort study of street-recruited injecting drug users

BACKGROUND

Injecting drug users (IDUs) are at risk of premature mortality. This study examined gender differences in mortality, risk factors, and causes of death among IDUs.

METHODS

In a 13-year cohort study including 172 street-recruited IDUs from Oslo, Norway in 1997, interview data was merged with the National Cause of Death Registry. Crude mortality rate (CMR) and indirect standardized mortality ratio (SMR) were estimated with 95% confidence intervals (CI). A log-logistic multivariate survival analysis model was estimated for the full sample. For a smaller data set (1.1.1998-31.12.2004) the influence of substitution treatment and prison were assessed using cox regression survival analysis.

RESULTS

Eight females and 37 males died. Acute intoxications were the most common cause of death. Women were more at risk in the short-term, but more protected in the long-term. CMR was 16.0 [95% CI 8.0, 31.9] for women and 26.0 [95% CI 18.0, 35.8]) for men. SMR was 39.4 [95% CI 0.2, 220.8]) for women and 21.3 [95% CI 5.7, 54.1] for men. More women injected heroin (98% vs. 88% [x2 = 3.5, p = 0.063]), used prescription drugs (73% vs. 52% [x2 = 5.6, p = 0.018]) and combined these to inject (45% vs. 26% [x2 = 5.9, p = 0.015]). Mixing prescription drugs in heroin injections, and sex work (only women) were associated with decreased survival time. There were no gender differences in access to substitution treatment, while significantly more men had been in prison (74% vs. 51% [x2 = 7.5, p = 0.006]). The instance of substitution treatment and prison significantly decreased the mortality risk. Prison release increased the risk, but not statistically significantly.

CONCLUSIONS

There were gender differences in mortality and risk factors; sex work and prison were gender specific risk factors. These factors should be investigated further to better design future preventive measures.