Fifteen percent of the drug users in the study died during the 10 years after admission to index treatment. This represents an annual mortality rate of 1.5: 2.0 for males and 0.6 for females. The main cause of death was overdose (68%). Being a male was by far the strongest predictor of all causes of mortality, but previous nonfatal overdoses, time in prison before baseline, as well dropout from index treatment were also related to increased mortality. A mortality rate of 1.5 is in line with most studies from Europe, which show mortality rates in the range of 1-2% per year among problem drug users.
As in other studies, the mortality rate among men was higher than among the women [1
]. The relative risk of mortality among the male drug abusers was 12 times higher compared to the age-adjusted general Norwegian male population [27
]. The corresponding number among the females was six times higher compared to the age-adjusted general female population [27
]. Males in the general population also have about twice the age-adjusted mortality risk as females [27
]. This difference in mortality between males and females underscores the importance of getting more gender specific knowledge about mortality in order to implement preventive measures especially tailored to address the specific needs of men and women.
The main cause of death was overdoses (68%), which is consistent with other studies [1
]. The majority died from heroin overdose but these deaths were also characterised by poly drug intoxications. Somewhat surprisingly, all but one of the women died from overdoses (90%) compared to 59% of the men. It seems that contrasting findings in studies of female drug abusers may be due to different designs, populations and data collected, even within the same country [10
]. The deceased females were on average four years younger than the males at time of death, they used fewer heroin’s than the males all through the observation period and fewer entered OMT. However, like the males they had a typical poly drug use, but with more use of benzodiazepines at index treatment. Autopsies of drug related deaths indicate that in many cases levels of heroin/morphine was low, but that poly drug use was common [30
]. The lack of association between fatal overdose and injecting drug use may be a consequence of the high percentage of injection users in the sample (83%).
Fifteen percent, and only males, died from what was classified as a violent death (traffic accidents, drowning, suicide, homicide etc.). Similar findings have been reported in other studies [2
]. In all these cases the use of other substances was also found. Only two persons died from AIDS, which is consistent with findings in countries with a low prevalence of HIV/AIDS [5
Time in prison prior to index treatment was a significant predictor of death after discharge from treatment. One possible explanation of this finding may be that this group of males was more antisocial and prone to taking risks, and both of these factors could lead to more crime and a more reckless lifestyle, including death by overdose. Even if MCMI antisocial PD was not a significant predictor of death in the regression analysis, there was a tendency for the deceased patients to have had higher scores on MCMI antisocial than the non-deceased clients. This finding is in line with another Norwegian study of drug users in which male gender, antisocial PD, and time in prison were related to death five years later [26
]. Important preventive strategies for males should therefore be tailored especially to antisocial males with a criminal record, as opposed to females who seem to have another personality style and more use of benzodiazepines. However, we need more knowledge about overdoses among females to indicate gender specific preventive strategies.
Having had one or more nonfatal overdoses before index treatment was also associated with death. This corresponds with the findings from the three-year follow-up Australian Treatment Outcome Study (ATOS), where previous nonfatal overdose experience was related to subsequent nonfatal overdoses [31
]. Having a history of nonfatal overdoses may also be associated with living a more reckless life.
In the present study the association between number of life-threatening overdoses and number of suicide attempts was not high, and in line with another prospective Norwegian treatment study of drug abusers, demonstrating that overdoses and suicide attempts may be distinguished on the basis of their disparate psychopathological risk variables and their different relationships to substances [17
]. Screening for both previous overdose experience and suicide attempts is advised to identify drug users who are at risk of overdoses and/or suicide attempts.
Patients who completed treatment had a lower risk of dying during the 10 year follow-up. Patients who stay in treatment for prolonged time have better outcomes than patients who drop out or spend less time in treatment [26
]. The first weeks after leaving inpatient treatment, when drug tolerance is low, comprise a critical period. Preventive strategies should therefore be specially tailored towards patients who leave treatment prematurely as well as towards patients at treatment completion.
The deceased patients reported more alcohol abuse prior to index treatment, and abuse of alcohol for more than five years before baseline was close to being a significant predictor of death (p=0.09). This tendency is consistent with other studies showing an association between abuse of alcohol and overdoses [4
]. However, only 18% in our total sample reported alcohol abuse before index treatment. In a recent Norwegian study of drug-induced deaths, alcohol was found in only 15% of the cases, whereas the most common combination of drugs was heroin and benzodiazepines (50%) [10
]. Whereas most Norwegian heroin injectors also use benzodiazepines, less than half reported combined use with alcohol [29
]. Our findings probably mirror the Norwegian pattern of drug use, with a high prevalence of heroin injection and poly drug use, often including a frequent use of benzodiazepines, but less use of alcohol.
As for preventive measures, there are no easy solutions at hand. The behavior of heroin users is often difficult to change. Those who may be in most need of organized treatment for their drug dependence as well as their other mental health disorders, may also be the ones who live under the most marginalized conditions and despair, and thus may both be difficult to reach and to keep in a rehabilitation process. A qualitative study of experiences with overdoses among Swedish heroin users is instructive in this context. The participants were aware of many of the common risk factors for overdoses. In spite of this, most overdoses occurred as a result of conscious risk-taking behavior. Search for the ‘ultimate rush’, as well as severe abstinence, anxiety and depression, feelings of indifference and dependency, and an unsafe, stressful environment were examples of factors that undermined the consideration of risks [16
]. The authors conclude that heroin overdoses cannot be fully understood simply by defining a variety of isolated factors. It is more important to bolster understanding of how heroin users perceive and evaluate the risk they are taking, and what circumstances and which emotions and motives influence risk-taking that may lead to overdose.
Treatment providers and healthcare authorities are advised to further strengthen preventive strategies. Patients in treatment should take part as early as possible in overdose prevention awareness programs with particular emphasis on the nature of overdose risk in the event of their leaving treatment prematurely. Drug users also represent an overlooked potential workforce; they can be interested in and willing to attend preventive training courses and to apply such knowledge when necessary [37
]. Programs to prevent fatal overdoses may be established and evaluated in the community, using resuscitation techniques as well as opioid antagonist medication such as naloxone [37
]. Preliminary results indicate lifesaving events through peer administration of naloxone [37
]. This research is still a young but promising field.
Better cooperation and communication between the health and social services are needed to identify and address the individuals, who are at particular risk, especially those characterized with multiple risk factors [10
]. Preventive strategies must be planned and carried out in treatment and community settings alike, and in continuous cooperation between active users of heroin, clients in treatment, the families of heroin users, and healthcare and social service authorities. Outreach strategies should also be implemented to minimize destructive life-style patterns by crisis interventions and the use of low-threshold measures [44
]. A wide range of preventive strategies is required if overdose deaths are to be reduced. Only a broad cooperation between all involved parties can help ensure that fewer heroin users, old and young alike, die from accidental or planned overdoses.