Global and Regional Trends in Multiple Sclerosis Incidence with Projections to 2030: A Joinpoint Regression Analysis...

Background: Multiple sclerosis (MS) constitutes one of the foremost neurological causes of disability among younger and middle-aged populations. Objective: This study aimed to examine global and regional trends in MS incidence from 1990 to 2021, with projections to 2030, using joinpoint regression and back-testing validation to ensure evidence-based scenario selection. Methods: Data were extracted from the Global Burden of Disease (GBD) 2021 study. Joinpoint regression was used to calculate annual percentage changes (APC) and average annual percentage changes (AAPC) for 1990-2021. A retrospective validation (back-testing) was conducted using data from 1990 to 2015 as the training period to project rates for 2016-2021, comparing predictive accuracy using mean absolute percentage error (MAPE) and root mean square error (RMSE). The method with lower error metrics was selected as the primary projection scenario for 2030, with the alternative retained for sensitivity analysis. Findings: Globally, the age-standardized incidence rate (ASIR) decreased slightly from 0.77 to 0.75 per 100,000 (1990-2021), while new cases increased by 49.9%. High socio-demographic index (SDI) (1.66) and EURO (2.57) regions had the highest ASIR in 2021, while low SDI (0.29) and Western Pacific Region (WPRO) (0.15) had the lowest. The back-testing identified APC as the preferred method in 10 of 12 regions (83.3%), with the lowest MAPE in AFRO (0.05%) and the highest discrepancy in South-East Asia Region (SEARO) (APC: 0.36% vs AAPC: 5.45%). Global ASIR is projected to decrease slightly to 0.747 by 2030, while SEARO (+12.3%) and low-middle SDI (+8.2%) regions show the largest increases. Sensitivity analysis confirmed robust projections globally, with trend reversals observed in SEARO and low SDI regions. Conclusion: Global MS incidence is projected to rise in most regions by 2030, particularly in transitioning economies and Southeast Asia. Strengthening diagnostic infrastructure and implementing context-specific health policies are urgently needed.