Multiple Sclerosis – The Current Picture: What Scientists Are Saying and Why It Matters

 This article is based on the large-scale study “The prevalence of MS in the United States: A population-based estimate using health claims data,” published in Neurology in 2019. The study is the result of collaborative work by a team of leading researchers and physicians from respected institutions across the U.S. and Canada. Among the contributors are Dr. Mitchell Wallin (Department of Veterans Affairs, Georgetown University), Dr. William Culpepper (University of Maryland), Dr. Lorene Nelson (Stanford University), Dr. Annette Langer-Gould (Kaiser Permanente), Dr. Ruth Ann Marrie (University of Manitoba), and others. These experts specialize in neurology, public health, and epidemiology, and are part of a special task force organized by the National Multiple Sclerosis Society (NMSS). The goal of this group is to provide a current, scientifically grounded, and nationally representative overview of the prevalence of multiple sclerosis (MS) in the U.S.

The information below answers five of the most important questions that patients and their families tend to ask, drawn directly from the conclusions and analysis of this leading epidemiological study.

"Multiple sclerosis is more common than previously thought—today, over 727,000 adults in the U.S. are living with this diagnosis."

What the Experts Are Saying

Why is it important to stay informed about current medical knowledge on multiple sclerosis?

Multiple sclerosis (MS) is one of the most common neurological diseases affecting young adults. It has a significant impact on the lives of patients and their families, and medical knowledge around its prevalence, diagnosis, and monitoring is evolving rapidly. This is why it’s so important for patients, their loved ones, and healthcare providers to have access to the most current, research-based information from leading scientists and physicians.

What follows are five key expert insights and scientific conclusions from the large-scale study on MS prevalence in the U.S., published in Neurology in 2019—each with explanation and guiding questions.

1. How many people are affected by multiple sclerosis? How common is the disease today?

Quote:

“The estimated 2010 prevalence of MS in the US adult population cumulated over 10 years was 309.2 per 100,000 (95% confidence interval [CI] 308.1–310.1), representing 727,344 cases.” “The estimated US national MS prevalence for 2010 is the highest reported to date and provides evidence that the north-south gradient persists.” (Wallin et al., 2019, p. e1033–e1035)

Explanation: According to the most recent estimates, compiled from various health insurance data sources, over 727,000 adults in the U.S. were living with MS as of 2010—significantly more than previous estimates suggested. This means MS is more prevalent than previously believed. The data also reveal a noteworthy geographic pattern: MS is more commonly diagnosed in northern states than in southern ones.

2. Who is most affected? Are there differences by gender or age?

Quote:

“During the same time period, the MS prevalence was 450.1 per 100,000 (95% CI 448.1–451.6) for women and 159.7 (95% CI 158.7–160.6) for men (female:male ratio 2.8). The estimated 2010 prevalence of MS was highest in the 55- to 64-year age group.” (Wallin et al., 2019, p. e1033)

Explanation: Women are nearly three times more likely to be affected by MS than men. The highest prevalence is seen in people aged 55 to 64. This may reflect both improved survival rates for people with MS and earlier detection due to modern diagnostic technologies.

3. What are the trends over time? Is the prevalence of MS increasing?

Quote:

“When coupled with prior estimates of the prevalence of MS in the US, our findings suggest that there has been a steady rise in the prevalence of MS over the past 5 decades, that the prevalence of MS remains higher for women than men, and that a north-south geographic gradient still persists.” (Wallin et al., 2019, p. e1035)

Explanation: Compared to earlier studies, the number of MS cases has steadily increased over the past 50 years. The reasons are likely complex and include not only a possible rise in risk but also better diagnostic tools and longer life expectancy among patients.

4. How is MS diagnosed, and how reliable are the tracking methods?

Quote:

“The optimal algorithm in terms of sensitivity, specificity, and simplicity required the accumulation of ≥3 MS-related hospitalizations, outpatient visits, or prescription release encounters for an MS disease-modifying therapy in any combination within a 1-year period. … When tested among individuals with at least 1 MS claim, the sensitivity of the MS algorithm was 86% to 92% and the specificity was 66% to 83%.” (Wallin et al., 2019, p. e1030)

Explanation: MS diagnoses and case tracking were conducted using a combination of hospitalizations, outpatient visits, and prescriptions for MS-specific therapies. The algorithm used had high sensitivity and reasonable specificity, meaning it's unlikely to miss many cases, though a small number of misclassifications can still occur.

5. What are the limitations of the data, and what does that mean for patients?

Quote:

“There are limitations to our approach. First, we did not include children, the Indian Health Service, the US prison system, or undocumented US residents in our prevalence estimates. … Furthermore, diagnosing pediatric MS is challenging; the performance of our proposed algorithm would need to be tested in this population given the recognized differences in relapse rates, more prominent cognitive impairment that may affect health care use, and reported differences in performance of algorithms across the pediatric and adult populations in other chronic diseases.” (Wallin et al., 2019, p. e1036–e1037)

Explanation: Despite its scale, the study does not include certain populations—children, Native American communities under the Indian Health Service, incarcerated individuals, or undocumented immigrants. Pediatric MS is particularly difficult to diagnose because it can present very differently than in adults.

Conclusions and Takeaways for Patients and Their Families

• MS is more common than previously believed. Early diagnosis and appropriate care are critical.

• Women and individuals aged 55–64 are the most affected.

• More people are living longer with MS, making long-term care and monitoring increasingly important.

• Diagnosis and case-tracking methods have improved, but challenges remain—especially in children and underrepresented groups.

• Patients and families should be aware of data limitations and seek a personalized approach to medical care.

Q&A

1. How has MS prevalence changed in recent years, and what’s behind those changes? 

Answer: The article shows that MS prevalence has risen significantly over the past five decades. This may be due not only to a real increase in cases but also to better diagnostic tools, evolving diagnostic criteria, and the introduction of new treatments. Additionally, more people are living longer with MS, which increases the overall number of patients at any given time.

2. Are there regional differences in MS prevalence, and what does that mean for patients? 

Answer: Yes, there's a clear north-south gradient in MS prevalence in the U.S.—people in northern states are more likely to have MS than those in the South. This may be linked to factors like sunlight exposure, vitamin D levels, genetics, and others, though the exact causes remain unclear. For patients, it’s important to understand that environmental and geographic factors can play a role in MS risk and should be part of future prevention and research strategies.

3. What sources of data are used to determine MS prevalence, and why is that important for patients? 

Answer: Researchers used large administrative databases from private and public health insurance systems, including military health records. These sources cover a large portion of the population, but some groups—like uninsured individuals, Native Americans, or prisoners—may be underrepresented. For patients, this means the statistics are quite accurate overall, but certain communities might be “invisible” in large-scale studies.

4. How reliable is MS information based on insurance data, and what are its limitations? 

Answer: The data is fairly reliable. The algorithm used to identify MS cases had high sensitivity (86–92%) and moderate specificity (66–83%). Still, some cases may be missed or misclassified, especially among those using alternative treatments or not part of mainstream healthcare systems. While these figures work well for general population estimates, individual experiences may vary.

5. What does “cumulative prevalence” mean, and why is it important to distinguish it from “annual prevalence”? 

Answer: The term "cumulative prevalence" refers to the number of people diagnosed with MS over a long period (e.g., 10 years), not just a single year. This gives a more accurate picture of the lifetime burden of the disease, since some people may go undiagnosed for years or be diagnosed late. For patients, this means that the true number of people living with MS is higher than annual data suggests—highlighting the need for long-term monitoring and support.

Conclusion

The data and conclusions presented in this article are entirely based on the 2019 publication by Wallin and colleagues—the most comprehensive and scientifically robust study on MS prevalence in the U.S. to date. By using massive health insurance databases and modern analytic methods, the authors offer a clearer, more accurate understanding of the disease’s frequency and characteristics.

For patients and their families, this information is invaluable: it provides a deeper sense of MS’s place in society, the factors that may influence its development, and the trends in diagnosis and monitoring. Trustworthy, science-based knowledge can help guide informed treatment decisions and empower individuals to seek support—both from medical professionals and from patient advocacy groups.

Source: Wallin MT et al. "The prevalence of MS in the United States: A population-based estimate using health claims data." Neurology. 2019;92:e1029–e1040. https://doi.org/10.1212/WNL.0000000000007035