Mortality among people who inject drugs: a systematic review and meta-analysis.

People who use drugs, especially by injection, are at higher risk of dying from both acute and chronic diseases, many of which are related to their drug use, than people who do not use these drugs. Fatal overdose and infection with human immunodeficiency virus (HIV) and other blood-borne viruses transmitted through shared needles and syringes are the most common causes of death in this group.1 Understanding causes of death is important when setting priorities for programmes designed to reduce deaths from the use of drugs. Longitudinal studies of people who inject drugs are critical for assessing the magnitude, nature and correlates of the risk of death in this population. A systematic review conducted in 2004 identified 30 prospective studies published between 1967 and 2004 that dealt with “problematic drug users” or people who inject drugs.2 These reviews have consistently shown that the practice of injecting drugs is associated with an elevated risk of death, particularly from the complications of HIV infection, drug overdose and suicide. Since these reviews were conducted, the number of studies examining mortality among cohorts of people who inject drugs has risen substantially. This has made it possible to perform fine-grained analyses that were not feasible in earlier reviews. Furthermore, those earlier reviews did not examine the potential impact of study-level variables, variation across countries, or of participant-level variables that could affect both mortality rates and differences in causes of death, yet study-level evidence suggests that males who inject drugs may be at higher risk of dying than females and that different types of drugs are associated with different risks of death.3–5 Findings from other reviews have also suggested that rates of death among people who are dependent on opioids are different from the rates of death observed in people who are dependent on stimulants such as cocaine and amphetamine type stimulants.3–5 In recent years the number of studies reporting on mortality among people who inject drugs has increased. Hence, the objective of this review was to determine the following: • overall crude mortality rates (CMRs) and excess deaths across cohorts of people who inject drugs, by sex; • causes of death across studies, particularly from drug overdose and acquired immunodeficiency syndrome (AIDS); differences in mortality rates and causes of death among HIV-positive (HIV+) and HIV-negative (HIV−) people who inject drugs; • differences in mortality rates across cohorts by geographical location and country income level; • mortality rates by type of drug injected (e.g. opioids versus stimulants); • mortality rates during in-treatment and off-treatment periods