Mapping the Global Footprint of Multiple Sclerosis: What Three Decades of Data Reveal About a Complex Disease

Multiple sclerosis (MS) is not only a neurological condition—it’s a complex, life-altering disease that reshapes the lives of millions worldwide. A new study published in Frontiers in Neurology (October 2024) by Safiri and colleagues provides one of the most comprehensive analyses yet of MS’s global impact, examining data from 204 countries between 1990 and 2019.

What is Multiple Sclerosis?
MS is an immune-mediated disorder where the body’s immune system mistakenly attacks the protective myelin sheath covering nerve fibers in the central nervous system. This demyelination disrupts communication between the brain and body, leading to a wide range of symptoms—from fatigue and vision loss to cognitive decline and mobility issues. Many of these symptoms are “invisible,” but they profoundly affect patients’ quality of life.

A Global Overview: Numbers That Matter
According to the study:

In 2019, there were 1.8 million people living with MS worldwide.

MS caused about 22,400 deaths and 1.2 million disability-adjusted life years (DALYs)—a measure combining years lost due to illness, disability, and premature death.

The global age-standardized prevalence rate was 21.3 per 100,000 people, representing a slight decline (~6%) since 1990.

While that decline might seem encouraging, the absolute number of people affected continues to rise, reflecting population growth and improved diagnostic capabilities.

Women Bear a Heavier Burden
Across all regions and age groups, women consistently showed higher prevalence rates than men. This aligns with previous research indicating that women are roughly three times more likely to develop MS.

Biological and hormonal factors—such as estrogen’s role in immune regulation—may partly explain this disparity. Interestingly, while women are more prone to developing MS, their long-term outcomes are not necessarily worse than men’s, suggesting that protective biological mechanisms may also be at play.

Regional Differences: Not All Burdens Are Equal
The study highlights stark geographic contrasts:

Highest prevalence: High-income North America (104 per 100,000), Western Europe (89 per 100,000), and Australasia (57 per 100,000).

Lowest prevalence: Oceania, East Asia, and Southeast Asia (around 2–4 per 100,000).

At the country level, the highest prevalence rates were found in Sweden, Norway, and Canada, while the lowest were recorded in Pacific Island nations such as Nauru and Kiribati.

These differences may stem from genetic predispositions, latitude (and thus vitamin D exposure), lifestyle factors, and variations in healthcare access and reporting systems.

The Socioeconomic Dimension
One of the study’s most striking findings is the non-linear relationship between MS burden and socioeconomic development.

Using the Sociodemographic Index (SDI), the researchers found that MS burden:

Increases slightly with SDI up to about 0.6 (moderate development),

Then rises sharply between 0.6 and 0.8 (high development),

And finally levels off or even declines at the highest SDI levels.

This suggests that as nations industrialize, factors like urban living, reduced sun exposure, dietary changes, and lifestyle behaviors (including smoking) may contribute to increased MS risk—until healthcare systems and preventive measures begin to offset these effects.

Smoking: A Major, Modifiable Risk Factor
Smoking emerged as a significant contributor to MS-related deaths and disabilities.

The study found that about 14% of the global MS burden is attributable to smoking, with higher rates in men.

Mechanistically, smoking promotes inflammation and oxidative stress, potentially triggering autoimmune reactions against myelin. Moreover, smokers with MS tend to experience faster disease progression and more severe brain damage.

The researchers emphasize that reducing smoking rates could prevent a notable share of future MS cases. Public health campaigns that link smoking cessation not only to heart or lung health—but also to brain health—could be powerful tools in MS prevention.

Beyond Smoking: Other Risk Factors and Treatments
While the Global Burden of Disease (GBD) dataset focused primarily on smoking, other well-documented MS risk factors include:

Vitamin D deficiency

Obesity

Physical inactivity

Genetic predispositions (especially HLA-DRB1 alleles)

Encouragingly, recent therapeutic advances have transformed MS management.

B cell-targeting treatments, such as anti-CD20 monoclonal antibodies (e.g., ocrelizumab), have significantly reduced relapse rates and slowed progression in both relapsing and primary progressive forms of MS. These innovations mark a new era in MS care, though access remains uneven globally.

The Bigger Picture: What This Means for Health Policy
Despite the modest global decline in age-adjusted rates, MS continues to impose a heavy global health and economic burden, especially in high-income countries.

The authors call for:

Integrating MS prevention and care into broader health systems,

Targeting modifiable risk factors (notably smoking and vitamin D deficiency),

And improving surveillance and diagnosis in low-resource settings.

Limitations and Future Directions
Like all GBD-based studies, this analysis relies on modeling and secondary data, which may underrepresent regions with weak health infrastructure. Furthermore, only smoking was included as a risk factor, leaving out other modifiable contributors like obesity and diet. Future iterations of GBD may expand the risk framework for a fuller picture of MS determinants. In Summary
Over three decades, the global age-standardized burden of MS has declined, yet the disease remains a major challenge, particularly for women and populations in high-income nations.

By tackling modifiable risks—chiefly smoking—and investing in early diagnosis and equitable access to modern therapies, we can hope to ease the global toll of MS in the years ahead.

Disclaimer: This blog post is based on the provided research article and is intended for informational purposes only. It is not intended to provide medical advice. Please consult with a healthcare professional for any health concerns.

References:
Safiri S., Ghaffari Jolfayi A., Mousavi S.E., Nejadghaderi S.A., Sullman M.J.M., & Kolahi A.-A. (2024). Global burden of multiple sclerosis and its attributable risk factors, 1990–2019. Frontiers in Neurology, 15:1448377. https://doi.org/10.3389/fneur.2024.1448377