Global trends and socioeconomic disparities in cancer burden among adolescents and young adults, 1990–2021

BACKGROUND: Adolescents and young adults (AYAs, 10-24 years) constitute a distinct cancer population in whom malignancy arises during critical life transitions yet leads to substantial long-term morbidity and socioeconomic consequences. However, their global cancer burden and risk-factor profile remain incompletely characterized, especially in low- and middle-income settings. METHODS: We conducted a secondary analysis of the Global Burden of Disease 2021 dataset, synthesizing estimates of cancer incidence, mortality, and disability-adjusted life years (DALYs) for 32 cancer types among AYAs across 204 countries and territories. Temporal trends (1990-2021) and associations with the socio-demographic index (SDI) were evaluated using log-linear and Spearman's correlation analyses. RESULTS: Globally, from 1990 to 2021, AYA cancer incidence rose slightly (+0.12% per year), while mortality and DALY rates declined (-1.02% per year). The fastest-rising incidence involved multiple myeloma (2.39% annually), breast, testicular, thyroid, and prostate cancers, whereas stomach, liver, esophageal, nasopharynx, and lung showed the steepest declines. In 2021, incidence correlated positively with SDI, but mortality and DALY rates correlated negatively. Modifiable risks accounted for 4.32% of DALYs, dominated by unsafe sex (2.54%) in low-SDI regions versus high body mass index (0.83%) and alcohol (0.64%) in higher-SDI settings. CONCLUSIONS: Global AYA cancer epidemiology reveals substantial geographical, temporal, and socioeconomic disparities. Rising incidence and burden of certain cancers highlight unmet prevention and diagnostic needs. Effective interventions, particularly targeting modifiable risks and promoting equitable healthcare access, are essential to reduce the global burden of AYA cancers.