There are many issues constraining a clear view of the outcomes of drug use. Causes of death varied over time, most strikingly with the introduction of HIV infection into the cohort and the dramatic effect of antiviral chemotherapy in the middle of the 1990 decade (Fig. 1).
Other trends reflect the long incubation period of hepatitis C which was introduced into the cohort in the early 1980’s when injecting first emerged in this population of, then, young people and the increase in drug related, liver and cardiovascular and respiratory causes of death.
The range of other conditions recorded on death certificates in this group is enormous and some are not directly related to drug injecting (Table 3).
Scrutiny of this extensive list illustrates the collateral damage often evident in caseloads attending drug treatment centres. Many, if not most, of these co existing conditions at the time of death are seen to be related to a lifestyle associated with poverty, inequalities, and drug use.
Drug use over a lifetime is, for most, an intermittent problem rather than following a linear pattern. Drug use and associated risks are often intermittent following a pattern of relapse and remission (17). There is an acute risk of, one off, hazards such as overdose, infection with a blood borne virus or a vascular event but there is also a cumulative risk over time resulting in premature fatal or morbid events.
Drug use is sometimes a poorly defined entity with many manifestations some more serious than others and some, like injecting behaviours, with the potential for immediate risk of death. Research often concentrates on short term problems and outcomes of treatment interventions and the impact of treatments such as agonist prescriptions, detoxification episodes and residential rehabilitation may not be immediate and therefore are more complicated to measure.
Recorded numbers of drug related deaths reported in the UK and Europe are largely about overdoses and take little account of the larger spectrum of mortality which should be attributed to drug related causes. Current definitions of a drug related death, in the UK, depend upon the presence of a drug, controlled under the Misuse of Drugs Act 1971, to be present at the time of death. The impact of blood borne viruses and bacterial infections as well as the longer term outcomes from conditions connected to current or past drug use remain absent from totals of death from drug causes.
This study suggests that there are several deaths attributed to drug injecting for every one that is recorded as an overdose. The delayed impact of infection with a blood borne virus or long term drug use has been missing from many studies but needs to be considered when assessing the burden of disease in this population.
Drug policy is often ideologically based and highly political in its construction. Evidence influences approaches to treatment and prevention only in response to crises and when damage cannot be ignored (18). Primary care and community based facilities are the ideal opportunity to engage and retain contact with people who have long term drug related issues and provides the possibility of a range of interventions including, but well beyond, the prescribing of Medically Assisted Opiate Agonist treatment.
The outcome of drug taking and the continuation or abstinence from illegal drugs is covered elsewhere in this cohort series but at the time of death and in the surviving group many continue to use a mixed economy of drugs, some prescribed and some accessed elsewhere. As in other studies the comorbid use of cigarettes and alcohol is common.
Strengths of this study
This study overcomes the issues of under classification of drug related deaths to an extent as it is a population based sample of people mainly recruited quite early in their lives and drug using careers and followed up in multiple ways. It therefore allows a clearer and more complete picture of the true population costs of drug use to be seen - and they are substantial over a life course - probably as substantial as the costs of other things we hear more about, like obesity and lack of exercise or poor diet. But like all those things the damage is intrinsically linked to and exacerbated by deprivation. This study is the first to systematically access death certificates in a cohort of people who have injected drugs. Drug users are sometimes difficult to define but the inclusion of a single group identified by the characteristic of injecting drugs gives a clear picture of a group of people with, arguably, the most serious risk factor associated with drug use. The study has the advantage of following a group over time and identifying a changing pattern of disease caused by drug policy, emergence of new diseases and the effect of drugs over a long time period. Whereas many previous studies quantify mortality to mainly overdoses of drugs this study adds a clearer, more complete, picture of the multisystem damage. The unique nature of the point in time when HIV entered the drug using culture distinguishes this cohort from others over the past 4 decades of drug use in the UK.
Weaknesses of this study
A cohort from one locality clearly has limited generalizability and must be interpreted in context of local and national variation in treatment policy. Not all patients were recruited at the same time and therefore their risks of death from time dependent variables such as HIV/AIDS and drug policy evolution differs. The variation in length of time spent injecting drugs was large some individuals injecting for a short period and others consistently over many years. All were included as risks such as blood borne virus transmission can occur during a single injecting event.