Divergent Global Trends in Mild and Moderate-to-Severe Traumatic Brain Injury: A Comprehensive Burden and Attribution Analysis from 1990 to 2021

Traumatic brain injury (TBI) represents a significant global health challenge, but a systematic, severity-stratified analysis of its epidemiology and risk factors is lacking. Using data from the Global Burden of Disease (GBD) 2021 study, this study compares the burden of mild TBI (mTBI) and moderate-to-severe TBI (msTBI) from 1990 to 2021. We analyzed incidence, prevalence, and years lived with disability (YLDs) for TBI across 204 countries and territories and by sociodemographic index (SDI) quintiles. Analysis included the characterization of age and sex distributions, assessment of temporal trends, and evaluation of risk factor attributions for both mTBI and msTBI. The results revealed that while the global age-standardized incidence rate (ASIR) of TBI declined, low-SDI regions experienced rising prevalence and YLD rates despite falling incidence. The ASIR of mTBI decreased significantly (average annual percentage change [AAPC]: -0.587; 95% confidence interval [CI]: -1.211-0.059), whereas the ASIR of msTBI showed no statistically significant decline (AAPC: -0.483; 95% CI: -1.235-0.275). The absolute number of mTBI cases peaked among young and elderly males, while the ASIR of msTBI increased with age in both sexes but remained consistently higher in males. Falls and road injuries remained the leading causes; however, the absolute number of msTBI cases due to these causes continued to rise. Notably, violence-related factors-including conflict and terrorism as well as police conflict and executions-were among the most rapidly increasing risk factors for both TBI subtypes. In conclusion, the global TBI burden is characterized by a stagnant crisis of msTBI, underscoring an urgent need for severity-specific prevention strategies that target high-risk mechanisms and populations to mitigate the devastating impact of msTBI worldwide.