Socio-demographic gradients in traumatic brain injury disability, severity and nutrition: a two-level analysis of the Global Burden of Disease Study 2023 and NHANES 2011–2014

Traumatic brain injury (TBI) is among the most consequential non-fatal outcomes of trauma, yet how its burden, severity and nutritional context are patterned by socio-demographic development remains incompletely characterised. We addressed this question at two levels. Using the Global Burden of Disease (GBD) Study 2023, we quantified the socio-demographic gradients of TBI disability across the five socio-demographic index (SDI) quintiles and characterised the severity composition of the TBI disability burden, its 1990-2023 trend and its cause-specific structure. Using pooled NHANES 2011-2014, we then examined, at the individual level, how reported TBI history among US adults aged 40 years and older varied by income, education, health insurance and food security, and whether dietary differences between adults with and without a TBI history persisted after socio-economic adjustment. The age-standardised TBI disability rate was almost twice as high in the high SDI quintile as in the low SDI quintile (113.68 versus 57.55 per 100,000 in 2023), a gap essentially unchanged since 1990. Moderate or severe injuries accounted for 72.5% of the TBI disability burden in the high SDI quintile versus 84.0-84.6% in the other four quintiles, rising in every quintile between 1990 and 2023. Among US adults, reported TBI history rose with educational attainment (11.9% below high school versus 17.3% above) and was most common in very food-insecure households (23.4%; adjusted odds ratio 1.71, 95% confidence interval 1.39-2.09); income showed no unadjusted gradient but a negative association after mutual adjustment. Unadjusted dietary differences between adults with and without a TBI history largely attenuated after socio-economic adjustment, with only fibre density remaining marginally lower (-0.35 g/1,000 kcal, 95% confidence interval -0.64 to -0.06). The moderate or severe share of the disability burden is a tractable, mortality-free monitoring indicator for injury prevention, and nutritional risk among food-insecure TBI survivors warrants clinical attention.