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Keywords:

  • Drug misuse;
  • mortality;
  • overdose;
  • surveillance monitoring

During the 1990s the number of drug-related deaths (acute poisonings) in the United Kingdom increased rapidly. Between 1993 and 2000 the number of deaths doubled from 864 to 1662 [1,2], precipitating the recognition that reducing drug misuse deaths was a public health priority [3]. The UK Advisory Council on the Misuse of Drugs recommended the creation of a new surveillance indicator to follow overdose trends, which was incorporated into the government's drugs strategy. A target was set to reduce deaths related to drug misuse by 20% by 2004 compared to a 1999 baseline [4]. As more than three-quarters of drug-related poisonings in the United Kingdom are opiate-related, expanding drug treatment options, especially methadone maintenance for problem opiate users, was seen as a critical overdose prevention measure [5]. UK and European indicators of drug-related deaths include deaths certified as due to drug use or misuse and include acute poisonings (overdose deaths) based on routine mortality statistics; the indicators exclude other deaths that may have been caused directly or indirectly by drug use but which cannot be attributed readily to drug use within routine statistics (such as infections, other injuries or chronic diseases) [1].

Early signs were very encouraging. Between 2001 and 2004, the government investment in specialist drug treatment doubled to over £250 million annually [6]. The volume of methadone prescriptions increased markedly, and there was a drop in the estimated number of deaths per 1000 patient-years treated with methadone [7]. The number of drug misuse deaths fell from 2001, and by 2003 the reduction in drug-related deaths had almost reached the target. However, in 2004 and 2005 there were sharp increases in drug misuse deaths, due largely to heroin overdose, meaning the government's target was not met [8,9].

The European context is presented in Fig. 1, which compares trends in overdose deaths in selected European countries with similar population sizes [10]. The figure shows drug misuse deaths per million population from 1993 to 2005 for England and Wales, Italy, Germany and Spain (Madrid, Barcelona, Valencia, Bilbao, Seville and Zaragoza only) based on routine mortality statistics. The drug-poisoning mortality rate in these six Spanish cities probably overestimates the rate for Spain overall, but is likely to provide an accurate representation of trends over time.

image

Figure 1. Drug misuse mortality rates per million population aged 15–64 in selected European countries, 1993 to 2005. For all countries rates are calculated using the Eurostat populations except for Spain, where data are shown for six cities (Madrid, Barcelona, Valencia, Bilbao, Seville and Zaragoza) and population data for these cities was provided by the 2001 Census

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By 2004/05 the drug misuse mortality rates in England and Wales was one of the highest in Europe. However, case definition and data extraction from mortality statistics varies between countries despite there being a common European definition [11], which may explain, in part, the difference in the size of the mortality rates between countries. There have been no changes in the compilation of statistics over time. More illuminating, therefore, and a salutary reminder to policy makers in England and Wales, is the difference in trends over time. In none of the other selected European countries did the overdose mortality rate double during the 1990s. Instead the evidence suggests that mortality rates declined in Spain and Italy and were stable in Germany. In addition, the other selected countries all achieved substantially greater reductions in drug-related deaths than England and Wales between 1999 and 2004/05, with Germany and Italy exceeding a 20% reduction and Spain (six cities) reducing the drug-related mortality rate by 17%.

Surveillance of deaths related to drug misuse is important for measuring the impact of interventions and for planning future harm minimization strategies, but it cannot answer more fundamental questions. What are the main drivers of drug overdose trends? Is the risk of overdose changing? Clearly, the number of overdose deaths is related to the interplay between changes in the size of the drug-using population and to their overdose mortality risk, with the latter related to other factors such as the proportion of IDU in treatment or changes in drug administration. The increase in overdose deaths during the 1990s in England and Wales was driven largely by increases in the prevalence of heroin use [2,8]. We have hypothesized that the reduction in overdose deaths from 2001 may have been the result of the rate of increase in treatment superseding any increase in the prevalence of drug misuse, and reducing the overall risk of overdose death [6,12].

However, in the United Kingdom since 1993 there has been no investment in large-scale longitudinal studies that could test this hypothesis and monitor whether the overall risk of overdose is declining, or the emergence or decrease of other forms of mortality among drug users. There have been a few, mainly city-based, studies in Europe [13], but the mortality patterns can be changing substantially and quickly [14–17] and large-scale cohort studies are needed in different European countries that can provide comparable information about overdose risk. Interpreting mortality statistics and trends in drug use is complex, and unlikely to lead to any firm conclusions without information on overdose risk. The figure shows that trends in overdose deaths vary between countries, implying differences in either the numbers of heroin injectors or overdose mortality risk. What we need to know, however, is whether (and why) the other European countries experienced a reduction in overdose mortality risk and/or prevalence of injecting drug use. We believe it is important now that we seek a better understanding of the mechanisms that underlie overdose mortality statistics.

References

  1. Top of page
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