The Global Burden and Trends of Premenopausal Breast Cancer by Modifiable Lifestyle Factors From 1990 to 2021 With Prediction Until 2039

BACKGROUND: Although breast cancer incidence has continued to rise worldwide, the disease burden of premenopausal breast cancer remains unclear, particularly given that attributable risk factors may vary across age groups and socioeconomic contexts. METHODS: Regional data on premenopausal breast cancer burden and related risk factors were derived from the updated Global Burden of Disease dataset for 1990-2021, with joinpoint regression applied to characterize time-dependent changes in disease burden by attributable factor. Disease burden up to 2039 was forecasted using a Bayesian age-period-cohort model, with further comparisons of risk-specific attributable burden. RESULTS: Countries with a high sociodemographic index (SDI) ranked highest for premenopausal breast cancer incidence (51.5 per 100,000 population), whereas countries with medium-low SDI showed the highest mortality and disability-adjusted life year (DALY) (7.0 per 100,000 population and 359.2 per 100,000 population, respectively). Disease burden has shown an upward trend in recent years, apart from high SDI areas, while this increase is expected to persist through 2039. Among the attributable risk factors assessed in the GBD framework, diet high in red meat accounted for the greatest share of attributable burden (11.2%), and the mortality and DALY attributed to red meat have both increased, with the largest increase occurring in low-middle SDI countries. CONCLUSIONS: The global burden of premenopausal breast cancer is increasing, with diet high in red meat contributing the greatest proportion of attributable burden among the assessed risk factors. Differences in major attributable risk factors across countries with different SDI levels highlight the need for tailored interventions to reduce the increasing burden of premenopausal breast cancer.