Comparative analysis of multiple sclerosis burden in China and India from 1990 to 2021 based on the Global Burden of Disease Study 2021.

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system and one of the leading causes of non-traumatic neurological disability among young adults worldwide. In recent years, an increasing number of cases have been reported in traditionally low-risk regions, including parts of Asia such as China and India. Our study aims to systematically compare the disease burden and long-term trends of MS in China and India from 1990 to 2021, and provide evidence for public health strategies in both countries. Data were obtained from the Global Burden of Disease Study 2021. Metrics including incidence, prevalence, mortality, and disability-adjusted life years (DALYs) related to MS in China and India were extracted. We calculated age-standardized rates for comparative analysis. Estimated annual percentage change (EAPC) and Joinpoint regression were used to assess trends. An age-period-cohort (APC) model was applied to disentangle the effects of age, period, and birth cohort. Bayesian APC modeling was used to project disease burden until 2040. India consistently demonstrated higher rates of incidence, prevalence, mortality, and DALYs than China. Joinpoint regression revealed a significant increase in DALYs in China between 2018 and 2021, whereas India exhibited a sustained upward trend over the study period. Decomposition analysis indicated that population growth was the primary driver of increased MS burden in both countries, with epidemiological changes playing an additional notable role in China. Projections suggested that prevalence in China will continue to rise due to extended patient survival, while most indicators in India are expected to decline. APC analysis identified clear age and period effects in both countries. Overall, both China and India face an increasingly heavy disease burden. In terms of age distribution, the disease burden in both countries is primarily concentrated among young- and middle-aged adults, and women are more affected. However, significant differences exist between the two nations in specific indicators and their underlying drivers. Projections indicate that all indicators in India show a downward trend. Although China exhibited an overall downward trajectory, certain sub-indicators are rising. It is potentially linked to improvements in China's diagnostic and treatment capabilities.