Thyroid disease burden among individuals aged 0-19 years in low-SDI countries, 1990-2035: a systematic analysis of the Global Burden of Disease Study 2023.

Background: Thyroid diseases can adversely affect growth, neurodevelopment, and long-term health during the first two decades of life. Because low Socio-demographic Index (SDI) countries may experience substantial disability despite comparable prevalence, clarifying this burden is essential for equitable pediatric endocrine service planning. This study aims to evaluate the prevalence and disability-adjusted life years (DALYs) burden of non-neoplastic thyroid diseases among individuals aged 0-19 years in 50 low-SDI countries from 1990 to 2023 and project trends to 2035. Methods: We used Global Burden of Disease (GBD) 2023 estimates derived from vital registration systems, household surveys, disease registries, hospital records, and published literature. Prevalence counts, prevalence rates, DALY counts, DALY rates, and age-sex-country-year-specific population denominators were extracted for individuals aged 0-19 years. Temporal trends were assessed using joinpoint regression and average annual percent change (AAPC). Age- and sex-specific patterns, Spearman correlations with SDI, slope index of inequality, concentration index, frontier efficiency gaps, and Bayesian age-period-cohort (BAPC) projections were analysed. All rates are reported per 100,000 population with 95% uncertainty intervals (UI). Results: The total population aged 0-19 years in the 50 low-SDI countries increased from approximately 440.5 million in 1990 to 847.7 million in 2023. Over the same period, prevalent cases increased from 6.22 million (95% UI: 4.38-8.80) to 11.39 million (95% UI: 7.87-16.58), while prevalence rates remained stable (AAPC =-0.06). Total DALYs increased from 0.19 million (95% UI: 0.13-0.29) to 0.32 million (95% UI: 0.23-0.49), whereas DALY rates decreased significantly (AAPC =-0.46). Females bore higher burden across all ages, peaking at 15-19 years, and neonates had persistently high DALY rates (130.2 per 100,000). Country-level heterogeneity was substantial; Haiti had the highest prevalence rate (2,752.0 per 100,000) and DALY rate (85.6 per 100,000), whereas Mali and Nepal showed the smallest efficiency gaps for prevalence and DALY rate, respectively. DALY rates negatively correlated with SDI (R =-0.36, P=0.01). By 2035, prevalent cases are projected to reach 18.37 million (95% UI: 0.18-36.56) and DALYs to reach 0.37 million (95% UI: 0.002-0.75). Conclusions: In low-SDI countries, stable prevalence rates mask a rapidly expanding absolute pediatric thyroid disease burden driven by population growth. Reducing avoidable disability requires integrating maternal iodine nutrition, dried blood spot newborn screening for congenital hypothyroidism, school-based detection for adolescents, and affordable levothyroxine and other essential thyroid medicines into universal health coverage benefit packages.