Background
Multiple sclerosis is the most common inflammatory neurological disease in young adults. The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) provides a systematic method of quantifying various effects of a given condition by demographic variables and geography. In this systematic analysis, we quantified the global burden of multiple sclerosis and its relationship with country development level.
Methods
We assessed the epidemiology of multiple sclerosis from 1990 to 2016. Epidemiological outcomes for multiple sclerosis were modeled with DisMod-MR version 2.1, a Bayesian meta-regression framework widely used in GBD epidemiological modeling. Assessment of multiple sclerosis as the cause of death was based on 13,110 site-years of vital registration data analyzed in the GBD's cause of death ensemble modeling module, which is designed to choose the optimum combination of mathematical models and predictive covariates based on out-of-sample predictive validity testing. Data on prevalence and deaths are summarized in the indicator disability-adjusted life years (DALYs), which was calculated as the sum of years of life lost (YLLs) and years of life lived with a disability. We used the Socio-demographic Index, a composite indicator of income per person, years of education, and fertility, to assess relations with development level.
Findings
In 2016, there were 2,221,188 prevalent cases of multiple sclerosis (95% uncertainty interval [UI] 2,033,866–2,436,858) globally, which corresponded to a 10.4% (9.1 to 11.8) increase in the age-standardized prevalence since 1990. The highest age-standardized multiple sclerosis prevalence estimates per 100,000 population were in high-income North America (164.6, 95% UI, 153.2 to 177.1), western Europe (127.0, 115.4 to 139.6), and Australasia (91.1, 81.5 to 101.7), and the lowest were in eastern sub-Saharan Africa (3.3, 2.9–3.8), central sub-Saharan Africa (2.8, 2.4 to 3.1), and Oceania (2.0, 1.71 to 2.29). There were 18,932 deaths due to multiple sclerosis (95% UI 16,577 to 21,033) and 1,151,478 DALYs (968,605 to 1,345,776) due to multiple sclerosis in 2016. Globally, age-standardized death rates decreased significantly (change −11.5%, 95% UI −35.4 to −4.7), whereas the change in age-standardized DALYs was not significant (−4.2%, −16.4 to 0.8). YLLs due to premature death were greatest in the sixth decade of life (22.05, 95% UI 19.08 to 25.34). Changes in age-standardized DALYs assessed with the Socio-demographic Index between 1990 and 2016 were variable.
Interpretation
Multiple sclerosis is not common but is a potentially severe cause of neurological disability throughout adult life. Prevalence has increased substantially in many regions since 1990. These findings will be useful for resource allocation and planning in health services. Many regions worldwide have few or no epidemiological data on multiple sclerosis, and more studies are needed to make more accurate estimates.
