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Article Excerpt
Drug use is one of the most important behavioral risk factors for burden of disease in developed countries. (1, 2) Most of this burden is due to premature mortality. (3) Research has identified an overall annual rate of mortality due to overdose at about 1-2% among drug users in Australia, Europe, and the United States. (4-7) Thus, the rates of premature mortality for drug addicts are much higher as compared to the general population of the same age. (8-16) According to a meta-analysis by English and colleagues (17) the standardized mortality ratio of drug users amounted to 13.2 (95% Confidence Interval (C.I.): 12.3-14.1). In other words, illicit drug users have a thirteen-fold higher mortality risk, as compared to the general population of the same age and sex.
Drug overdose is a major cause of premature mortality among populations of illegal drug users. (18-21) Research studies have identified a variety of risk factors that are associated with the risk of drug overdose. People who die accidentally from drug overdoses tend to be young adults with a mean age in the late 20s to early 30S, (22-28) are typically male, (29-33) and usually have several years of drug use experience. (34-37) Most are daily or almost daily users of drugs, (38, 39) and the majority administer drugs by injection. (40-45) In addition, poverty, (46, 47) homelessness, (48) co-administration of alcohol and benzodiazepines with opioids, (49-52) recent changes in patterns of use affecting tolerance to drugs (e.g., recent release from prison, after enforced or voluntary abstinence), (53-56) impaired physical health status, (57, 58) depression, (59, 60) and a lifetime history of drug overdose (61, 62) are all factors associated with greater risk for overdose death.
Recent research has shown that nonfatal drug overdose is also quite common among drug users. (63-66) More than half of injection drug users (IDUs) reported a history of drug overdose. (67) Survivors of drug overdose suffer from many complications such as renal failure, lung infections, cardiovascular complications, and cognitive impairments, (68, 69) all of which may lead to premature mortality among illegal drug users. However, such effects are hard to quantify on a population basis due to the lack of larger studies.
Drug users appear to be at an elevated risk of suicide as compared to the general population. (70-72) One study indicated that suicide is 14 times greater among heroin users as compared to the general population. (73) However, most drug overdoses do not appear to be suicide attempts. (74-78) Only 5% of fatal heroin overdoses that occurred in Australia over a five-year period were classified as suicides. (79) Similarly, 92% of methadone maintenance patients reported that their recent overdose was accidental rather than intentional. (80) Recent literature has found the prevalence of intentional overdose to range from 1% to 49%. (81) This significant variation in prevalence may be the result of heterogeneous samples (e.g. treatment vs. non-treatment populations; habitual versus occasional users) as well as lack of a universal definition of intentional overdose across studies.
Drug use, especially injection drug use (IDU), also causes an additional number of indirect deaths due to infection (82-85) and other diseases. (86-88) The prevalence of human immunodeficiency virus infection in the IDU population in Canada varies from 11% to 32%, (89, 90) and hepatitis B ranges from 25% to 35%. (91, 92) The prevalence of hepatitis C infection among IDUs varies more widely--from 16% to 88%. (93, 94)
Despite the number of individual studies on mortality due to drug use, systematic Canadian research on the drug-attributable mortality in Canada has been very limited (for an exception see "Morbidity and Mortality attributable to alcohol tobacco, and illicity drug use in Canada"). (95) To increase the evidence base and inform public health action in order to prevent drug-related mortality, this study was designed to assess overdose mortality, other drug-related mortality, and calculate potential years of life lost for Canada in 2002.
Methods
In the following paragraphs, two elements necessary for estimating drug-attributable deaths are described:
* Determination of risk relationships and attributable fractions
* Outcome measurement.
Establishing mortality attributable to illegal drug use
The number of drug-attributable overdose-deaths and suicides involving illegal drugs in Canada 2002 (except North West Territories and Nova Scotia, which both reported data for the latest available year, 2001) was obtained from each provincial Chief Coroner's office. It has been shown in the past that coroners' data give a more realistic picture of overdose deaths in Canada than the official mortality statistics of Statistics Canada, (96) which seem to miss a considerable portion of drug-attributable overdoses. The data obtained from the coroners' offices were thus used to estimate the overall number of deaths from drug overdose, and were also used to estimate drug-related suicides.
Unfortunately, most of the provincial Chief Coroners' reports did not have age/sex specifications for drug overdose and suicides. When missing data, we statistically estimated these distributions according to sex-age groups distribution from Statistics Canada. Detailed provincial coroners' data on age/gender distribution, manner of death, and type of drugs are available from the authors.
There is no universal international definition of drug-induced or drug-attributable deaths. This creates considerable methodological problems in comparing statistics on drug-related mortality. In this study, the definition of "drug overdose deaths" was based on the coroners' description, i.e. all overdose deaths involving, at minimum, one illicit drug was counted. Most of the individual descriptions involved two or more illicit drugs, and it is impossible to attribute causality to one substance over the other.
Overall mortality data for 2002 were obtained from Statistics Canada. Based on the International Classification of Diseases, revision 10 (ICD-10), we used the categories of death from accidental overdoses, and death undetermined as to intent due to misuse of drugs, to estimate overdose deaths from that source. According to ICD-10 guidelines, the term "drug" is a substance classified as a drug, medicament or biological substance which might be used for medical or therapeutic purposes, or to produce a psychoactive effect. This term excludes alcohol, tobacco, and volatile...
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