20-year trends in Australian methamphetamine-related deaths: An age–period–cohort–interaction analysis

Background: Australia has one of the highest estimated rates of methamphetamine use globally. Over the past two decades, methamphetamine-related deaths in Australia have quadrupled, mainly due to drug toxicity and suicide among people aged in their 30s and 40s. Previous analysis of Australian methamphetamine-related deaths covered limited timeframes and cause categories, and there has been no exploration into the effects of changing cohorts on methamphetamine mortality. This paper provides comprehensive insights across 20 years of evolving cohort patterns among methamphetamine-related deaths in Australia.

Methods: An age–period–cohort–interaction (APC-I) analysis of Australian methamphetamine-related deaths (2001-2020) by cause extracted from the National Coronial Information System, a database of deaths reported to the coroner in Australia and New Zealand.

Results: Between 2001 and 2020, methamphetamine-related deaths were classified as being due to unintentional drug toxicity (52.3%), intentional self-harm including poisoning (24.9%), unintentional injury (15.8%) and natural causes (9.2%). APC-I analyses show varying age effects across the four death causes, with unintentional injuries peaking among people aged 19 to 30, drug toxicity and intentional self-harm peaking among those aged 23 to 46, and natural cause deaths peaking among individuals aged 39 to 50. The period effects are largely consistent across all causes of death, where they gradually rise from 2001 to 2011, followed by a sharp increase until 2016, and then stabilise. Observed cohort effects among all four causes of death showed a peak among individuals born between 1962 and 1982, indicating a higher-than-average risk of mortality among ‘Generation X’, with risk declining among subsequent generations.

Conclusion: Our APC-I analyses reveal that, despite different age profiles across the various causes of death, cohort effects suggest a single generation (Generation X) is predominantly experiencing the increase in methamphetamine-related mortality observed in Australia. Understanding this cohort trend is crucial for developing targeted and effective harm reduction, prevention, and treatment programs.