Burdens and risk factors for mortality in adolescents and young adults aged 10-24 years in Australia and comparison with OECD countries between 2000 and 2021: Global Burden of Disease Study 2021.

Introduction: Adolescents are considered the healthiest population of all age groups, yet they are vulnerable to illnesses and deaths from preventable causes. We aimed to investigate the burden of morbidity, mortality and risk factors for mortality among adolescents and young adults (10-24 years) in Australia compared with the Organisation for Economic Co-operation and Development (OECD) countries. Methods: We accessed the Global Burden of Disease (GBD) Study 2021 data for OECD countries, including Australia, between 2000 and 2021. Country and age-specific estimates with 95% uncertainty intervals were obtained from the GBD Compare and Results Tool for all-cause mortality and disability-adjusted life years (DALYs). The top 15 level 3 risk factors for mortality for adolescents and young adults were investigated, with rates reported per 100 000 population. Annualised rates of change (ARoC) in mortality and DALY rates were estimated using a log-linear model to quantify temporal trends between distinct time periods. Causes of death by age groups, sex and year for other diseases were measured using the Cause of Death Ensemble model. Results: Between 2000 and 2021, mortality rates in adolescents and young adults decreased in Australia and across OECD regions, with substantial reductions (47.1 in 2000 vs 27.9 in 2021) in Australia. DALYs decreased slightly (11 850.2 in 2000 vs 10 363.9 in 2021), ranking Australia eighth among OECD countries in 2021. The ARoC in Australia showed a decline in the rate of mortality and DALYs by 2.48% and 0.64%, respectively. Overall, OECD countries experienced a slower decline, with an ARoC of 0.92% for mortality and 0.04% for DALYs from 2000-2021. Young adults (20-24 years) had higher mortality and DALYs than other age groups. In 2021, males in Australia and OECD countries had higher mortality rates, while Australian females had more DALYs than males. Alcohol and drug use were the leading risk factors for death. Conclusion: Adolescent and young adult mortality in Australia has declined more than the OECD average, with minimal reduction in disease burden. Disparities in mortality rates and morbidity burden continue to grow across countries, age groups and genders due to the limited focus on males and young adults. This study calls for comprehensive health strategies that address these disparities to reduce the disease burden in young adults, specifically among males.