Global Burden of Early-onset Cancers Attributable to Behavioral Risk Factors from 1990 to 2021: Population-based Study

Introduction: Behavioral risk factors contribute to early-onset cancers, which are rising globally. This study quantifies their attributable burden and trends from 1990 to 2021. Methods: Data on deaths, disability-adjusted life years (DALYs), and rates from the Global Burden of Disease Study 2021 were analyzed for early-onset cancers linked to behavioral risks. Trends were evaluated using the estimated annual percentage change (EAPC) across sex, age, and sociodemographic index (SDI) groups. Results: Global deaths and DALYs from behavioral risk factors for early-onset cancers increased between 1990 and 2021, but mortality and DALY rates declined significantly (EAPC: 1.15%/year). In 2021, smoking and unsafe sex were the leading risk factors, with cervical cancer accounting for the highest burden. Most behavioral risk factors demonstrated decreasing trends, except for low physical activity, and lip and oral cavity cancer burdens increased. Males exhibited faster declines in mortality (EAPC: −1.42% vs. −0.84%) and DALY rates (EAPC: −1.45% vs. −0.85%) than females. Age specific trends showed that unsafe sex predominated the younger population (15–39 years), while smoking was more prevalent in older groups (40–49 years). Meanwhile, high SDI countries achieved steeper declines (mortality EAPC: −2.21%, DALYs EAPC: −2.17%) compared to low SDI countries, where several risk factors increased. Smoking was the leading risk factor in high-SDI regions, whereas unsafe sex was predominant in low-SDI regions. Conclusion: Smoking and unsafe sex remain major contributors to early-onset cancers, with pronounced sex–age–SDI inequalities. While high-SDI regions improved outcomes, low-SDI regions faced increasing risks. Targeted interventions are urgently needed to reduce behavioral risks, particularly in low-resource settings and younger population, to address global health inequities.