Back-projection estimates of the number of dependent heroin users in Australia

The characteristics of people who inject drugs in the United Kingdom: changes in age, duration, and incidence of injecting, 1980-2019, using evidence from repeated cross-sectional surveys

BACKGROUND AND AIMS

Mortality and drug treatment data suggest that the median age of people who inject drugs is increasing. We aimed to describe changes in the characteristics of people injecting drugs in the United Kingdom (UK).

DESIGN

Repeat cross-sectional surveys and modelling.

SETTING

Low-threshold services in the United Kingdom such as needle and syringe programmes.

PARTICIPANTS

A total of 79 900 people who recently injected psychoactive drugs in the United Kingdom, recruited as part of the Unlinked Anonymous Monitoring Survey (England, Wales, Northern Ireland, 1990-2019) and Needle Exchange Surveillance Initiative (Scotland, 2008-2019).

MEASUREMENTS

Age of people currently injecting, age at first injection, duration of injecting (each 1990-2019) and estimates of new people who started injecting (1980-2019).

FINDINGS

In England, Wales and Northern Ireland between 1990 and 2019, the median age of people injecting increased from 27 (interquartile range [IQR], 24-31) to 40 (IQR, 34-46); median age at first injection increased from 22 (IQR, 19-25) to 33 (IQR, 28-39); and median years of injecting increased from 7 (IQR, 3-11) to 18 (IQR, 9-23). Values in Scotland and England were similar after 2008. The estimated number that started injecting annually in England increased from 5470 (95% prediction interval [PrI] 3120-6940) in 1980 to a peak of 10 270 (95% PrI, 8980-12 780) in 1998, and then decreased to 2420 (95% PrI, 1320-5580) in 2019. The number in Scotland followed a similar pattern, increasing from 1220 (95% PrI, 740-2430) in 1980 to a peak of 3080 (95% PrI, 2160-3350) in 1998, then decreased to a 270 (95% PrI, 130-600) in 2018. The timing of the peak differed between regions, with earlier peaks in London and the North West of England.

CONCLUSIONS

In the United Kingdom, large cohorts started injecting psychoactive drugs in the 1980s and 1990s and many still inject today. Relatively few people started in more recent years. This has led to changes in the population injecting drugs, including an older average age and longer injecting histories.

Estimating the number of people who inject drugs and syringe coverage in Australia, 2005-2016

BACKGROUND

Effective targeting of harm reduction programs for people who inject drugs (PWID) requires timely and robust estimates of the size of this population. This study estimated the number of people who inject drugs on a regular basis in Australia, calculated syringe coverage per person and the proportion of their injections covered by a sterile needle and syringe.

METHODS

We used trends in indicators of injection drug use to extend the 2005 estimate of the population of people who regularly inject drugs from 2005 to 2016. Included indicators were lifetime/recent injection of illicit drugs, drug-related arrests, drug-related seizures, accidental deaths due to opioids, opioid-related hospital admissions/separations and new diagnoses of hepatitis C virus infection among those aged 15-24 years. Syringe distribution and frequency of injection data were used to assess syringe coverage per PWID and the proportion of their injections covered by a sterile syringe.

RESULTS

The estimated number of people who regularly inject drugs in Australia increased by 7%, from 72,000 in 2005 to 77,270 in 2016. The annual number of syringes distributed per person increased 34%, from 470 syringes in 2005 to 640 syringes in 2016. Syringe coverage per injection first exceeded 100% in Australia in 2013.

CONCLUSIONS

Despite Australia's high syringe coverage by international standards, the number of syringes distributed is likely to be only narrowly meeting demand. It is critical that needle syringe programs be provided with sufficient resources to continue their role as the key intervention required to prevent HIV and HCV transmission among PWID.

Illegal Drug-Attributable Mortality and Potential Years of Life Lost in Canada 2002: Implications for Prevention and Policy

The article estimates the deaths and years of life lost due to use of illegal drugs in Canada in the year 2002. In 2002, for Canada, 1,695 deaths were attributable to illegal drug use, 0.8% of all deaths: 1,183 of men (1.0%) and 512 in women (0.5%). Main causes of illegal drug use-attributable death were drug overdose, suicide, and hepatitis C. In 2002 in total, 62,110 years of life were lost prematurely, 42,306 years among men and 19,805 years among women. Illegal drug use constitutes a major contributor to the burden of mortality in Canada. A mixture of prevention and harm reduction measures is proposed to reduce the burden of mortality associated with drug use.

Modeling the initiation of others into injection drug use, using data from 2,500 injectors surveyed in Scotland during 2008-2009

The prevalence of injection drug use has been of especial interest for assessment of the impact of blood-borne viruses. However, the incidence of injection drug use has been underresearched. Our 2-fold aim in this study was to estimate 1) how many other persons, per annum, an injection drug user (IDU) has the equivalent of full responsibility (EFR) for initiating into injection drug use and 2) the consequences for IDUs' replacement rate. EFR initiation rates are strongly associated with incarceration history, so that our analysis of IDUs' replacement rate must incorporate when, in their injecting career, IDUs were first incarcerated. To do so, we have first to estimate piecewise constant incarceration rates in conjunction with EFR initiation rates, which are then combined with rates of cessation from injecting to model IDUs' replacement rate over their injecting career, analogous to the reproduction number of an epidemic model. We apply our approach to Scotland's IDUs, using over 2,500 anonymous injector participants who were interviewed in Scotland's Needle Exchange Surveillance Initiative during 2008–2009. Our approach was made possible by the inclusion of key questions about initiations. Finally, we extend our model to include an immediate quit rate, as a reasoned compensation for higher-than-expected replacement rates, and we estimate how high initiates' quit rate should be for IDUs' replacement rate to be 1.

Statistical estimations for Plasmodium vivax malaria in South Korea

OBJECTIVE

To calculate the numbers of weekly infections and prevalence of malaria, and to predict future trend of malaria incidences in South Korea.

METHODS

Weekly incidences of malaria for 13 years from the period 2001-2013 in South Korea were analyzed. The back-calculation equations were used with incubation period distributions. The maximum likelihood estimation for Poisson model was also used. The confidence intervals of the estimates were obtained by a bootstrap method. A regression model for time series of malaria incidences over 13 years was fitted by the non-linear least squares method, and used to predict futuretrend.

RESULTS

The estimated infection curve is narrower and more concentrated in the summer than in the incidence distribution. Infection started around the 19th week and was over around the 41st week. The maximum weekly infection 110 was obtained at the 29th week. The prevalence at the first week was around 496 persons, the minimum number was 366 at 22nd week, and the maximum prevalence was 648 at 34th week. Prevalence drops in late spring with people that falling ill and had had long incubation periods and rose in the summer with new infections. Our future forecast based on the regression model was that an increase at year 2014 compared to 2013 may reach a peak (at maximum about 70 weekly cases) at year 2015, with a decreasing trend after then.

CONCLUSIONS

This work shows that back-calculation methods could work well in estimating the infection rates and the prevalence of malaria. The obtained results can be useful in establishing an efficient preventive program for malaria infection. The method presented here can be used in other countries where incidence data and incubation period are available.

Internet search and krokodil in the Russian Federation: an infoveillance study

BACKGROUND

Krokodil is an informal term for a cheap injectable illicit drug domestically prepared from codeine-containing medication (CCM). The method of krokodil preparation may produce desomorphine as well as toxic reactants that cause extensive tissue necrosis. The first confirmed report of krokodil use in Russia took place in 2004. In 2012, reports of krokodil-related injection injuries began to appear beyond Russia in Western Europe and the United States.

OBJECTIVE

This exploratory study had two main objectives: (1) to determine if Internet search patterns could detect regularities in behavioral responses to Russian CCM policy at the population level, and (2) to determine if complementary data sources could explain the regularities we observed.

METHODS

First, we obtained krokodil-related search pattern data for each Russia subregion (oblast) between 2011 and 2012. Second, we analyzed several complementary data sources included krokodil-related court cases, and related search terms on both Google and Yandex to evaluate the characteristics of terms accompanying krokodil-related search queries.

RESULTS

In the 6 months preceding CCM sales restrictions, 21 of Russia's 83 oblasts had search rates higher than the national average (mean) of 16.67 searches per 100,000 population for terms associated with krokodil. In the 6 months following restrictions, mean national searches dropped to 9.65 per 100,000. Further, the number of oblasts recording a higher than average search rate dropped from 30 to 16. Second, we found krokodil-related court appearances were moderately positively correlated (Spearman correlation=.506, P≤.001) with behaviors consistent with an interest in the production and use of krokodil across Russia. Finally, Google Trends and Google and Yandex related terms suggested consistent public interest in the production and use of krokodil as well as for CCM as analgesic medication during the date range covered by this study.

CONCLUSIONS

Illicit drug use data are generally regarded as difficult to obtain through traditional survey methods. Our analysis suggests it is plausible that Yandex search behavior served as a proxy for patterns of krokodil production and use during the date range we investigated. More generally, this study demonstrates the application of novel methods recently used by policy makers to both monitor illicit drug use and influence drug policy decision making.

ANKK1, TTC12, and NCAM1 polymorphisms and heroin dependence: importance of considering drug exposure

CONTEXT

The genetic contribution to liability for opioid dependence is well established; identification of the responsible genes has proved challenging.

OBJECTIVE

To examine association of 1430 candidate gene single-nucleotide polymorphisms (SNPs) with heroin dependence, reporting here only the 71 SNPs in the chromosome 11 gene cluster (NCAM1, TTC12, ANKK1, DRD2) that include the strongest observed associations.

DESIGN

Case-control genetic association study that included 2 control groups (lacking an established optimal control group).

SETTING

Semistructured psychiatric interviews.

PARTICIPANTS

A total of 1459 Australian cases ascertained from opioid replacement therapy clinics, 531 neighborhood controls ascertained from economically disadvantaged areas near opioid replacement therapy clinics, and 1495 unrelated Australian Twin Registry controls not dependent on alcohol or illicit drugs selected from a twin and family sample.

MAIN OUTCOME MEASURE

Lifetime heroin dependence.

RESULTS

Comparison of cases with Australian Twin Registry controls found minimal evidence of association for all chromosome 11 cluster SNPs (P ≥ .01); a similar comparison with neighborhood controls revealed greater differences (P ≥ 1.8 × 10(-4)). Comparing cases (n = 1459) with the subgroup of neighborhood controls not dependent on illicit drugs (n = 340), 3 SNPs were significantly associated (correcting for multiple testing): ANKK1 SNP rs877138 (most strongly associated; odds ratio = 1.59; 95% CI, 1.32-1.92; P = 9.7 × 10(-7)), ANKK1 SNP rs4938013, and TTC12 SNP rs7130431. A similar pattern of association was observed when comparing illicit drug-dependent (n = 191) and nondependent (n = 340) neighborhood controls, suggesting that liability likely extends to nonopioid illicit drug dependence. Aggregate heroin dependence risk associated with 2 SNPs, rs877138 and rs4492854 (located in NCAM1), varied more than 4-fold (P = 2.7 × 10(-9) for the risk-associated linear trend).

CONCLUSIONS

Our results provide further evidence of association for chromosome 11 gene cluster SNPs with substance dependence, including extension of liability to illicit drug dependence. Our findings highlight the necessity of considering drug exposure history when selecting control groups for genetic investigations of illicit drug dependence.

Treatment of hepatitis C as prevention: a modeling case study in Vietnam

BACKGROUND

Treatment of hepatitis C (HCV) is very effective, achieving a cure in 50-90% of patients. Besides its own good for individuals, this most likely translates in reduced transmission, but this phenomenon has yet to be fully explored.

METHODS AND FINDINGS

In this mathematical modeling study done in the context of Vietnam, we estimated the public health benefit that HCV therapy for injecting drug users (IDUs) may achieve. Treatment coverage of 25, 50 and 75% of chronically HCV-infected IDUs (4 years into infection) is predicted to reduce the chronic HCV viremia prevalence respectively by 21, 37 and 50%, 11 years after full scale up to the intended coverage. At a constant 50% coverage level, earlier treatment, 3, 2, and 1 year into infection is predicted to reduce the chronic HCV viremia prevalence by 46, 60 and 85%. In these later 3 scenarios, for every 100 treatment courses provided, a total of respectively 50, 61 and 94 new infections could be averted. These benefits were projected in the context of current low coverage of methadone maintenance therapy and needles/syringes exchange programs, and these services expansion showed complementary preventive benefits to HCV therapy. The program treatment commitment associated with the various scenarios is deemed reasonable. Our model projections are robust under adjustment for uncertainty in the model parameter values.

CONCLUSIONS

In this case study in Vietnam, we project that treatment of HCV for injecting drug users will have a preventative herd effect in addition to curing patients in need for therapy, achieving a substantial reduction in HCV transmission and prevalence.

What data are available on the extent of illicit drug use and dependence globally? Results of four systematic reviews

BACKGROUND

We systematically reviewed availability and quality of data on the prevalence of use and dependence on meth/amphetamine, cannabis, cocaine and opioids.

METHODS

Multiple search strategies: (a) peer-reviewed literature searches (1990-2008) using methods recommended by the Meta-analysis of Observational Studies in Epidemiology (MOOSE) group; (b) systematic searches of online databases; (c) Internet searches to find other published evidence of drug use; (d) repeated consultation and feedback from experts around the globe; (e) a viral email sent to lists of researchers in the illicit drug and HIV fields. Data were extracted and graded according to predefined variables reflecting quality of data source.

RESULTS

Qualitative evidence of illicit drug use and dependence was found for most countries, which hold over 98% of the world's population aged 15-64 years. Countries where use was identified but prevalence estimates had not been made (evidence of drug supply, trafficking, reports of use, treatment data) were mainly from Asia, Africa, the Middle East, and Oceania. Estimates of the prevalence of use were located in 77 countries for meth/amphetamine, 95 for cannabis, 86 for cocaine and 89 for opioids. Dependence prevalence estimates existed in very few countries; 9 meth/amphetamine dependence estimates, 7 cannabis dependence estimates, 5 cocaine dependence estimates, and 25 opioid dependence estimates were located.

CONCLUSIONS

Data on the extent of meth/amphetamine, cannabis, cocaine and opioid use and dependence must be improved in quality and coverage. Dependence estimates are lacking even in high income countries that have required resources. Responses to illicit drug dependence require better estimates of its scale.

Systematic review of prospective studies investigating "remission" from amphetamine, cannabis, cocaine or opioid dependence

AIMS

To review and summarize existing prospective studies reporting on remission from dependence upon amphetamines, cannabis, cocaine or opioids.

METHODS

Systematic searches of the peer-reviewed literature were conducted to identify prospective studies reporting on remission from amphetamines, cannabis, cocaine or opioid dependence. Searches were limited to publication between 1990 and 2009. Reference lists of review articles and important studies were searched to identify additional studies. Remission was defined as no longer meeting diagnostic criteria for drug dependence or abstinence from drug use; follow-up periods of at least three years were investigated. The remission rate was estimated for each drug type, allowing pooling across studies with varying follow-up times.

RESULTS

There were few studies examining the course of psychostimulant dependence that met inclusion criteria (one for amphetamines and four for cocaine). There were ten studies of opioid and three for cannabis dependence. Definitions of remission varied and most did not clearly assess remission from dependence. Amphetamine dependence had the highest remission rate (0.4477; 95%CI 0.3991, 0.4945), followed by opioid (0.2235; 95%CI 0.2091, 0.2408) and cocaine dependence (0.1366; 95%CI 0.1244, 0.1498). Conservative estimates of remission rates followed the same pattern with cannabis dependence (0.1734; 95%CI 0.1430, 0.2078) followed by amphetamine (0.1637; 95%CI 0.1475, 0.1797), opioid (0.0917; 95%CI 0.0842, 0.0979) and cocaine dependence (0.0532; 95%CI 0.0502, 0.0597).

CONCLUSIONS

The limited prospective evidence suggests that "remission" from dependence may occur relatively frequently but rates may differ across drugs. There is very little research on remission from drug dependence; definitions used are often imprecise and inconsistent across studies and there remains considerable uncertainty about the longitudinal course of dependence upon these most commonly used illicit drugs.

The impact of a supervised injecting facility on ambulance call-outs in Sydney, Australia

AIMS

Supervised injecting facilities (SIFs) are effective in reducing the harms associated with injecting drug use among their clientele, but do SIFs ease the burden on ambulance services of attending to overdoses in the community? This study addresses this question, which is yet to be answered, in the growing body of international evidence supporting SIFs efficacy.

DESIGN

Ecological study of patterns in ambulance attendances at opioid-related overdoses, before and after the opening of a SIF in Sydney, Australia.

SETTING

A SIF opened as a pilot in Sydney's 'red light' district with the aim of accommodating a high throughput of injecting drug users (IDUs) for supervised injecting episodes, recovery and the management of overdoses.

MEASUREMENTS

A total of 20,409 ambulance attendances at opioid-related overdoses before and after the opening of the Sydney SIF. Average monthly ambulance attendances at suspected opioid-related overdoses, before (36 months) and after (60 months) the opening of the Sydney Medically Supervised Injecting Centre (MSIC), in the vicinity of the centre and in the rest of New South Wales (NSW).

RESULTS

The burden on ambulance services of attending to opioid-related overdoses declined significantly in the vicinity of the Sydney SIF after it opened, compared to the rest of NSW. This effect was greatest during operating hours and in the immediate MSIC area, suggesting that SIFs may be most effective in reducing the impact of opioid-related overdose in their immediate vicinity.

CONCLUSIONS

By providing environments in which IDUs receive supervised injection and overdose management and education SIF can reduce the demand for ambulance services, thereby freeing them to attend other medical emergencies within the community.

Estimating incidence trends in regular heroin use in 26 regions of Switzerland using methadone treatment data

Background

Regional incidence trends in regular heroin use are important for assessing the effectiveness of drug policies and for forecasting potential future epidemics.

Methods

To estimate incidence trends we applied both the more traditional Reporting Delay Adjustment (RDA) method as well as the new and less data demanding General Inclusion Function (GIF) method. The latter describes the probability of an individual being in substitution treatment depending on time since the onset of heroin use. Data on year of birth, age at first regular heroin use and date of admission to and cessation of substitution treatment was available from 1997 to 2006 for 11 of the 26 regions (cantons) of Switzerland. For the remaining cantons, we used the number of patients in 5-year age group categories published in annual statistics between 1999 and 2006.

Results

Application of the RDA and GIF methods on data from the whole of Switzerland produced equivalent incidence trends. The GIF method revealed similar incidence trends in all of the Swiss cantons. Imputing a constant age of onset of 21 years resulted in almost equal trends to those obtained when real age of onset was used. The cantonal incidence estimates revealed that in the mid 80s there were high incidence rates in various regions distributed throughout all of the linguistic areas in Switzerland. During the following years these regional differences disappeared and the incidence of regular heroin use stabilized at a low level throughout the country.

Conclusion

It has been demonstrated that even with incomplete data the GIF method allows to calculate accurate regional incidence trends.

Estimating prevalence of injecting drug use: a comparison of multiplier and capture-recapture methods in cities in England and Russia

We consider the question of what method should be recommended to estimate the prevalence of injecting drug use (IDU); and compare multiplier and capture-recapture (CRC) methods of estimating prevalence of injecting drug use (IDU). The prevalence of injecting drug use in four cities (Brighton, Liverpool, London and Togliatti) was estimated using similar methods: covariate capture-recapture (CRC) and multipliers. The multipliers, generated either from a community recruited survey or historical/literature-based, were applied to a range of 'benchmarks': specialist drug treatment, arrests, accident and emergency department (A&E), syringe exchange, HIV tests and opiate overdose deaths. The CRC estimates were assumed to be 'preferred/gold standard' [2,304 (95% confidence interval 1,514 - 3,737) in Brighton, 2,910 (2,546 - 4,977) in Liverpool, 16,782 (13,793 - 21,620) in 12 London boroughs and 15,039 (12,696 - 18,515) male IDU in Togliatti]. The ranges given by the multiplier estimates obtained through the community survey varied from 200 to 770 in Brighton, 530 to 1,300 in Liverpool, 2,900 to 10,600 in London and 12,400 to 91,000 in Togliatti. Several multipliers gave implausible results, lower than the observed data collected for another benchmark, and in the three English cities all these multiplier estimates were below the lower 95% confidence interval of the CRC estimate. In Togliatti, only one multiplier estimate was close to the preferred CRC estimates, with the rest implausibly high. The multiplier estimates based on historical/literature multipliers also ranged widely from 390 to 4,800 for Brighton, from 1,645 to 2,800 in Liverpool, from 4,650 to 12,600 in the 12 London boroughs and 12,800 to 32,000 in Togliatti. In the three UK cities the mortality multiplier estimates were closest to the capture-recapture estimates. The study was a practical demonstration comparing a range of multiplier estimates with a single CRC study. In almost all the individual comparisons the multiplier estimates performed poorly. CRC methods should be preferred as the means of estimating numbers of drug users with multiplier methods being used with caution and only where CRC is not possible.

Heroin users in Australia: population trends

The aim of this paper is to identify certain important population trends among heroin users in Australia for the period 1971 - 97, such as: population growth, initiation, i.e. the number who were initiated to heroin in a given year, and quitting, i.e. the number that quit using heroin. For this purpose, we summarize and extract relevant characteristics from data from National Drug Strategy Household Survey (NDSHS 1998) conducted in Australia in 1998. We devise a systematic procedure to estimate historical trends from questions concerning past events. It is observed from our findings that the size of the heroin user population in Australia is in a sharp increase, especially from the early 1980s onwards. The general trend obtained for the period 1971 - 97 is strikingly similar to that obtained by Hall et al. (2000) for the dependent heroin user population in Australia, even though their study was based on different datasets and a different methodology. In our reconstruction of the time history we also detect a levelling-off prior to 1990. Initiation is also observed to be on a sharp increase. The latter trend is accompanied by a similar trend of quitting, perhaps indicating a relatively short heroin use career. A sharp decrease in both initiation and quitting is observed after 1990. In conclusion, in the case of the trend in the population of heroin users a high rate of growth has been identified that is consistent with the existing literature. In the process, we demonstrated that even a static survey such as NDSHS 1998 can, sometimes, be used to extract historical (dynamic) trends of certain important variables.

Estimating the prevalence of ex-injecting drug use in the population

Injecting drug use is the main route of transmission for the hepatitis C virus in the developed world. Knowledge about the characteristics of the past and current injecting drug user (IDU) population is therefore vital in order to understand the epidemiology of hepatitis C. The IDU population is ;hard to reach' and hence most epidemiological studies have concentrated on estimating current IDU prevalence, whilst little is known about the potentially large pool of ex-injectors. We demonstrate a method for estimating the proportion of ex-users in the population, by considering injecting drug use as a time-to-event process. We show how unbiased estimates of injecting duration and historical patterns in injecting initiation can be derived from a sample of ex-IDUs obtained from a population survey, and how such data lead to estimates of the proportion of ex-IDUs in the population. Finally, we show how to obtain estimates of the prevalence of ex-IDUs by using additional information on the prevalence of current IDUs.

New challenges for mathematical and statistical modeling of HIV and hepatitis C virus in injecting drug users

Injecting drug users are not only driving blood-borne transmission of HIV and hepatitis C virus but also likely drive sexual transmission of HIV in large parts of the world. Mathematical and statistical modeling can provide important insights in these epidemiological processes and on the potential impact of interventions but have been little used to date. This review aims to discuss the potential areas of application of modeling in the field of viral infections in injecting drug users. After reviewing key examples of published modeling work on HIV and hepatitis C virus in injecting drug users, we discuss recent developments in the epidemiology, diagnosis, treatment and prevention of these infections. In particular, new methods for the diagnosis of early HIV infection, new antivirals for a more effective treatment of HIV, hepatitis B and hepatitis C virus infections, new concepts in design and surveillance of interventions for drug users and increasing possibilities of molecular typing of pathogens are changing the questions and decisions for public health policy makers who deal with drug-related infectious diseases. Research including mathematical modeling is needed to understand the impact of new diagnostic tools, new treatment options and combined intervention strategies on the epidemiology of viral infections in injecting drug users. Methodological advances in mathematical modeling are required to adequately approach some of the ensuing research questions. Modeling has much to offer for solving urgent policy questions, but current levels of funding in modeling research are insufficient and need to be scaled up to make better use of these possibilities.

Estimating heroin epidemics with data of patients in methadone maintenance treatment, collected during a single treatment day

AIMS

Effects of differing drug policies are difficult to evaluate, because time trends in the spread of heroin use, the most problematic illicit drug world-wide, are unknown in almost all countries. We aimed to develop a simple method to estimate these dynamics with data that can be gathered from patients in substitution treatment within a single day.

DESIGN

We tested the assumption that being in substitution treatment on any day depends solely upon individual time since onset of regular heroin use (following a 'general inclusion function'). We used data from the case register for substitution treatments in the canton of Zurich (1992--2004), comprising 9518 patients, to model a 'general inclusion function'. Applying this function, we calculated 30 incidence curves for heroin dependence, each with data of one of 30 randomly chosen treatment days between 1992 and 2004.

FINDINGS

Incidence modelling led to 30 similar curves, and therefore our hypothesis was corroborated. Additionally, our approach also revealed a restricted access to substitution treatment in the early 1990s and a decline in demand due to the introduction of heroin-assisted treatment from 1994 onwards.

CONCLUSIONS

In the canton of Zurich, the probability of being in substitution treatment can be described by a 'general inclusion function', and therefore dynamics of heroin epidemics can be estimated based on data of a single treatment day. Adaptation of our function to areas with a more restricted access to substitution treatment may permit these estimations also in other regions or countries. Thus, our approach facilitates the urgently needed assessment of the effects of different drug policies.

Incidence of heroin use in Zurich, Switzerland: a treatment case register analysis

BACKGROUND

Switzerland has been criticised for its liberal drug policy, which could attract new users and lengthen periods of heroin addiction. We sought to estimate incidence trends and prevalence of problem heroin use in Switzerland.

METHODS

We obtained information about first year of regular heroin use from the case register of substitution treatments in the canton of Zurich for 7256 patients (76% of those treated between 1991 and March, 2005). We estimated the proportion of heroin users not yet in substitution treatment programmes using the conditional lag-time distribution. Cessation rate was the proportion of individuals leaving substitution treatment programmes and not re-entering within the subsequent 10 years. Overall prevalence of problematic heroin use was modelled as a function of incidence and cessation rate.

FINDINGS

Every second person began their first substitution treatment within 2 years of starting to use heroin regularly. Incidence of heroin use rose steeply, starting with about 80 people in 1975, culminating in 1990 with 850 new users, and declining substantially to about 150 users in 2002. Two-thirds of those who had left substitution treatment programmes re-entered within the next 10 years. The population of problematic heroin users declined by 4% a year. The cessation rate in Switzerland was low, and therefore, the prevalence rate declined slowly. Our prevalence model accords with data generated by different approaches.

INTERPRETATION

The harm reduction policy of Switzerland and its emphasis on the medicalisation of the heroin problem seems to have contributed to the image of heroin as unattractive for young people. Our model could enable the study of incidence trends across different countries and thus urgently needed assessments of the effect of different drug policies.

The contribution of research to Australian policy responses to heroin dependence 1990-2001: a personal retrospection

Periodic public concern about heroin use has been a major driver of Australian drug policy in the four decades since heroin use was first reported. The number of heroin-dependent people in Australia has increased from several hundreds in the late 1960s to around 100,000 by the end of the 1990s. In this paper I do the following: (1) describe collaborative research on heroin dependence that was undertaken between 1991 and 2001 by researchers at the National Drug and Alcohol Research Centre; (2) discuss the contribution that this research may have made to the formulation of policies towards the treatment of heroin dependence during a period when the policy debate crystallized around the issue of whether or not Australia should conduct a controlled trial of heroin prescription; and (3) reflect on the relationships between research and policy-making in the addictions field, specifically on the roles of investigator-initiated and commissioned research, the interface between researchers, funders and policy-makers; and the need to be realistic about the likely impact of research on policy and practice.

Modelling hepatitis C virus incidence, prevalence and long-term sequelae in Australia, 2001

BACKGROUND

To plan an appropriate public health response to the hepatitis C virus (HCV) epidemic requires that estimates of HCV incidence and prevalence, and projections of the long-term sequelae of infection, are as accurate as possible. In this paper, mathematical models are used to synthesize data on the epidemiology and natural history of HCV in Australia to estimate HCV incidence and prevalence in Australia to end 2001, and project future trends in the long-term sequelae of HCV infection.

METHODS

Mathematical models of the HCV epidemic in Australia were developed based on estimates of the pattern of injecting drug use. Estimates of HCV infections due to injecting drug use were then adjusted to allow for HCV infections resulting from other transmission routes. Projections of the long-term sequelae of HCV infection were obtained by combining modelled HCV incidence with estimates of the progression rates to these outcomes.

RESULTS

It was estimated that there were 210 000 (lower and upper limits of 157 000 and 252 000) people in Australia living with HCV antibodies at the end of 2001, with HCV incidence in 2001 estimated to be 16 000 (11 000-19 000). It was estimated that 6500 (5000-8000) people were living with HCV-related cirrhosis in 2001, that 175 (130-210) people developed HCV-associated liver failure, and that there were 50 (40-60) incident cases of HCV-related hepatocellular carcinoma (HCC). It was estimated that in 2001 22 500 quality adjusted life years were lost to chronic HCV infection, the majority (77%) in people with early (stage 0/1) liver disease.

DISCUSSION

Model-based estimates were broadly consistent with other sources of information on the HCV epidemic in Australia. These models suggest that the prevalence of HCV-related cirrhosis and the incidence of HCV-related liver failure and HCC will more than triple in Australia by 2020.

Drug-related mortality and fatal overdose risk: pilot cohort study of heroin users recruited from specialist drug treatment sites in London

Fatal overdose and drug-related mortality are key harms associated with heroin use, especially injecting drug use (IDU), and are a significant contribution to premature mortality among young adults. Routine mortality statistics tend to underreport the number of overdose deaths and do not reflect the wider causes of death associated with heroin use. Cohort studies could provide evidence for interpreting trends in routine mortality statistics and monitoring the effectiveness of strategies that aim to reduce drug-related deaths. We aimed to conduct a retrospective mortality cohort study of heroin users recruited from an anonymous reporting system from specialist drug clinics. Our focus was to test whether (1). specialist agencies would agree to participate with a mortality cohort study, (2). a sample could be recruited to achieve credible estimates of the mortality rate, and (3). ethical considerations could be met. In total, 881 heroin users were recruited from 15 specialist drug agencies. The overall mortality rate of the cohort of heroin users was 1.6 (95% confidence interval [CI], 1.1 to 2.2) per 100 person-years. Mortality was higher among males, heroin users older than 30 years, and injectors, but not significantly higher after adjustment in a Cox proportional hazard model. Among the 33 deaths, 17 (52%) were certified from a heroin/methadone or opiate overdose, 4 (12%) from drug misuse, 4 (12%) unascertained, and 8 (24%) unrelated to acute toxic effects of drug use. Overall, the overdose mortality rate was estimated to be at least 1.0 per 100 person-years. The standardized mortality ratio (SMR) was 17 times higher for female and male heroin users in the cohort compared to mortality in the non-heroin-using London population aged 15-59 years. The pilot study showed that these studies are feasible and ethical, and that specialist drug agencies could have a vital role to play in the monitoring of drug-related mortality.

Trends in drug overdose deaths in England and Wales 1993-98: methadone does not kill more people than heroin

AIMS

To test the hypothesis that methadone is responsible for a greater increase in overdose deaths than heroin, and causes proportionally more overdose deaths than heroin at weekends.

DESIGN AND SETTING

Multivariate analysis of 3961 death certificates mentioning heroin, morphine and/or methadone held on the Office for National Statistics drug-related poisoning mortality database from 1993 to 1998 in England and Wales.

MEASUREMENTS

Percentage increase in deaths by year by drug, odds ratio (OR) of dying at the weekend from methadone-related overdose compared to dying from heroin/morphine overdose.

FINDINGS

From 1993 to 1998, annual opiate overdose deaths increased from 378 to 909. There was a 24.7% (95% confidence interval (CI) 22-28%) yearly increase in heroin deaths compared to 9.4% (95% CI 6-13%) for methadone only. This difference was significant (P < 0.001 by test of interaction) after adjustment for sex, age group, polydrug use, area of residence and underlying cause of death. The largest number of deaths occurred on Saturday (673). The OR of death from methadone overdose on Saturday and Sunday was 1.48 (95% CI 1.29-1.71) for methadone-only deaths compared to dying from heroin/morphine at the weekend after adjustment for other covariates, but the OR was not significant (1.09, 95% CI 0.95-1.25) if the weekend was defined as Friday and Saturday.

CONCLUSIONS

There was no evidence that the threefold increase in deaths over time was due to methadone. There was equivocal support only for the hypothesis that there was an excess of deaths from methadone at weekends. Increased interventions to prevent overdose among injectors in England and Wales are long overdue.

Supply control and harm reduction: lessons from the Australian heroin 'drought'

AIMS

To examine the effects of supply-side drug law enforcement on the dynamics of the Australian heroin market and the harms associated with heroin.

SETTING

Around Christmas 2000, heroin users in Sydney and other large capital cities in Australia began reporting sudden and significant reductions in the availability of heroin. The changes, which appear to have been caused at least in part by drug law enforcement, provided a rare opportunity to examine the potential impact of such enforcement on the harm associated with heroin.

DESIGN

Data were drawn from a survey of 165 heroin users in South-Western Sydney, Australia; from the Drug Use Monitoring in Australia (DUMA) project; from NSW Health records of heroin overdoses; and from the Computerized Operational Policing System (COPS) database.

FINDINGS

Heroin price increased, while purity, consumption and expenditure on the drug decreased as a result of the shortage. The fall in overall heroin use was accompanied by a significant reduction in the rate of overdose in NSW. However, the health benefits associated with the fall in overdose may have been offset by an increase in the use of other drugs (mainly cocaine) since the onset of the heroin shortage. There does not appear to have been any enduring impact on crime rates as a result of the heroin 'drought'.

CONCLUSION

Supply control has an important part to play in harm reduction; however, proponents of supply-side drug law enforcement need to be mindful of the unintended adverse consequences that might flow from successfully disrupting the market for a particular illegal drug.

Deaths by unintentional illicit drug overdose in Italy, 1984-2000

AIM

To determine whether there has been an increase in deaths by overdose in Italy, as elsewhere in the Western world, over the past fifteen years.

METHOD

This study's conclusions are based on analysis of official data on overdose deaths attributed to illicit drug addiction and abuse (ICD-9 codes 304 and 305) from 1984 to 2000, drawn from two archives of drug abuse information: the Direzione Centrale per i Servizi Antidroga (DADE) of the Italian Ministry of the Interior (1984-2000), and the Health Statistics held at the Italian Central Statistics Institute (ISTAT) (1984-1997). Mortality rates have been calculated for both genders in the following age groups: 15-24, 25-34, and 35-44 years.

RESULTS

Official data indicate that there has been a steady increase in the number of deaths by overdose in Italy over recent 15 years. This trend has affected both genders, but is more evident among males. Over the whole period females had consistently lower overdose rates than males. In both genders the age group 35-44 was subject to the highest mortality rate increase over the study period, however, the highest overdose rates for both males and females were observed in the 25-34 age group. Consistently higher rates were witnessed in the northern regions of Italy with an overall increase across all latitudes. However, the greatest increase over the study period occurred in the South. In 5190 cases evaluated by the Italian Forensic Toxicology Group, 95.9% of deaths were attributed to heroin, but in about half of these, mixtures of three or more substances (heroin, benzodiazepines, cannabinoids, cocaine, methadone) were found in the deceased at doses that were likely to have contributed to death.

CONCLUSIONS

The increase observed in the rates of death by overdose is likely to be a reflection of increased use of illicit drugs in the general population. Reporting practice by forensic pathologists might explain the extent of attribution of cause of death to heroin. Drop-out from addiction treatment is a commonly observed antecedent of fatal opioid overdose, therefore, caution is required when establishing treatment protocol for patients. Interventions that aim specifically at improving patient compliance with medical and psychiatric therapies should be favoured.