Global, regional, and national burden of nonalcoholic fatty liver disease (NAFLD) among people aged 15 to 49 years from 1990 to 2021, with projections to 2050: A systematic analysis based on the 2021 global burden of disease study

Nonalcoholic fatty liver disease (NAFLD) is a growing global health concern due to its increasing prevalence and potential to cause serious liver complications. NAFLD is rising among people aged 15 to 49 years, a critical age group for workforce and reproduction, yet its burden and trends in this population remain insufficiently studied. This study aimed to evaluate the prevalence, incidence, mortality, and disability-adjusted life years (DALYs) associated with NAFLD in this age group across 204 countries and territories from 1990 to 2021, using data from the global burden of disease (GBD) 2021 database. Trends in disease burden were assessed using average annual percentage change (AAPC), with stratified analyses by sex, age, and socio-demographic index (SDI). Bayesian age-period-cohort (BAPC) models were employed to project future trends and quantify the contributions of major risk factors. By 2021, the global incidence, prevalence, mortality, and DALY rates of NAFLD in people aged 15 to 49 years were 909.48 per 100,000 persons (95% UI: 647.19-1216.77), 16,580.43 per 100,000 persons (95% UI: 12,851.14-20,866.60), 0.45 per 100,000 persons (95% UI: 0.27-0.72), and 22.77 per 100,000 person-years (95% UI: 13.74-35.81), respectively. Between 1990 and 2021, both incidence and prevalence increased, whereas mortality and DALYs remained relatively stable. NAFLD burden declined as SDI increased, peaking at an SDI of approximately 0.6 before gradually decreasing. Males consistently exhibited higher burden than females. The leading contributors to age-standardized mortality were tobacco use and elevated fasting glucose, with the impact of metabolic risk factors rising over time. Burden increased with age, with incidence peaking at age 22.5 and subsequently declining. By 2050, the number of new NAFLD cases among people aged 15 to 49 years is projected to reach 48.29 million globally, with the number of deaths expected to rise to 23,396.5. The substantial increase in NAFLD burden over the past 3 decades highlights the urgent need for early screening and diagnosis. These findings may inform future public health planning aimed at reducing the disease burden among people aged 15 to 49 years.