Background

Drug-induced deaths represent a critical public health problem in Australia. Understanding long-term temporal trends and seasonal variation in daily death rates may inform targeted prevention and harm minimisation strategies; however, these patterns have not previously been examined at the national level.

Methods

We conducted a time series analysis using national mortality records and population estimates. The study included all unintentional and intentional drug-induced deaths among individuals aged ≥15 years in Australia between 1 January 2000 and 31 December 2021. Temporal trends in daily death rates were examined separately for unintentional and intentional deaths, including long-term (entire study period), seasonal (within-year), and weekly (within-week) patterns, as well as the impact of national and state public holidays and major sporting events. Model selection followed a data-driven approach using the Bayesian Information Criterion (BIC), incorporating polynomial functions and harmonic terms. Secondary analyses were stratified by sex, age group, and state or territory of usual residence.

Results

Between 2000 and 2021, 21,693 unintentional and 7,831 intentional drug-induced deaths were recorded. Temporal and seasonal trends were identified for unintentional deaths, wherein rates were highest in winter months and on weekends. The New Year period was associated with increased daily rates (+24%) and the Easter period demonstrated a trend towards lower rates (-16%) for unintentional deaths, compared to average daily death rates. Rates of intentional death rates were more consistent across time intervals, with only small increases in summer and on Monday-Tuesday. There was no evidence of changes in intentional death rates associated with holidays/sporting events.

Conclusion

Substantial seasonal and temporal variation was evident for unintentional drug-induced death rates in Australia, highlighting opportunities for targeted prevention and harm minimisation strategies during high-risk periods. Intentional drug-induced death rates showed minimal seasonal variation, underscoring the need for sustained, year-round prevention efforts.