Relapsing-Remitting MS Facts and Statistics: What You Need to Know

Relapsing-remitting multiple sclerosis (RRMS), the most common type of multiple sclerosis, affects 85% to 90% of people with MS. RRMS is associated with exacerbations (relapses) of new or worsening neurological symptoms followed by periods of symptom recovery (remission).

This article will review key facts and statistics about relapsing-remitting MS, including disease prevalence and how it affects life expectancy. It will also provide insight into the possible causes of RRMS and how it's diagnosed.

Relapsing-Remitting MS Overview

In MS, the immune system attacks the insulating myelin layer of nerve fibers within the brain, spinal cord, and optic nerves. When myelin is damaged, nerve signaling is impaired. This malfunction leads to various symptoms like numbness, fatigue, weakness, and blurry vision.

Most people with MS initially are diagnosed with RRMS. They experience relapses that last at least 24 hours and typically continue for days or weeks before they go away or improve.

As with other types of MS, relapsing-remitting MS cannot be reversed or cured. Periods of remission, however, can be lengthened by taking disease-modifying therapies (DMTs). Also, powerful anti-inflammatory drugs called corticosteroids can shorten relapses.

How Common Is RRMS?

The estimated prevalence of MS in the United States is nearly 1 million adults. RRMS occurs in around 87% of these individuals.

Worldwide, the estimated prevalence of MS is 2.8 million individuals. It has increased from 2.3 million in 2013.

RRMS by Ethnicity

Since 2013, MS prevalence has increased across most ethnicities, including populations within the United States, Middle East, North Africa, Canada, Australia, and Europe. It's unclear whether the increased prevalence is due to improved detection or if environmental factors are at play.

Historically, MS had been most commonly diagnosed in White people of northern European or Scandinavian ancestry. Recent investigation, however, shows a similarity in MS prevalence among both Black and White people.

The finding that MS, including RRMS, is more common in the Black population than previously thought likely indicates that MS has been underrecognized and understudied in Black people, as opposed to being an emerging or rare condition.

RRMS by Age and Gender

RRMS is typically detected in early adulthood, at a median age of 30. About 5% of cases are diagnosed at 50 or older. 

RRMS can manifest in children or adolescents, although only 3%–10% of MS cases occur before age 16. Less than 1% of MS cases manifest before age 10. Most of those with pediatric MS (98%) follow a relapsing-remitting course.

MS is 2 to 3 times more common in females than males across all racial and ethnic groups. Interestingly, females with MS tend to have an earlier onset of disease than males, and they typically show less progression of disability.

Causes of RRMS and Risk Factors

The exact cause of MS, including RRMS, remains unknown. However, it's believed that a complex interplay of genetics, various environmental factors, and abnormal immune system response is involved. By 2021, more than 233 genes had been linked with MS. 

Factors associated with the development of MS include:

• Low sunlight exposure and vitamin D deficiency
• Past infection with Epstein-Barr virus
• Tobacco smoking
• Obesity in adolescence
• The gut microbiome (the organisms that live in your digestive tract)

Some factors increase a person's chances of having an MS relapse. These factors include infection, stress, low vitamin D levels, and the postpartum period (the time after giving birth).

What Are the Mortality Rates for RRMS?

Research has consistently found a higher mortality rate for people living with relapsing-remitting multiple sclerosis compared to the general population.

For example, one 2017 Norwegian study examining nearly 1,400 people diagnosed with MS over a 60-year time frame had a seven-year shorter lifespan and a nearly threefold higher risk of death than the general population.

Despite the higher mortality rate in MS, people generally live longer than ever, likely due to various improvements in health care and lifestyle habits. Specifically, taking a disease-modifying drug for MS is associated with a lower risk of death compared to receiving no treatment.  

Interestingly, investigators in the 2017 Norwegian study also found that people with RRMS had a six-year longer life expectancy than people with primary progressive MS (PPMS).

PPMS is a relatively rare type of MS associated with slowly worsening symptoms and disability over time in the absence of relapses. The finding suggests that RRMS offers a better outlook than PPMS.

Screening and Early Detection

There is no screening test for RRMS nor a single blood or imaging test that can diagnose RRMS.

To diagnose RRMS, a neurologist (a physician specializing in nervous system disorders) collects data from a person's medical history, neurological exam, and various tests, including:

• A magnetic resonance imaging (MRI) of the brain and spinal cord
  
• A spinal tap (lumbar puncture)
• Evoked potential tests (measures the electrical activity in the brain)
• Blood tests to rule out conditions with similar symptoms (e.g., vitamin B12 deficiency)
  

Individual MS relapses are detected clinically (a person's symptoms) and confirmed by the presence of one or more enhancing lesions (areas of inflammation) on a brain or spinal cord MRI scan.

The neurological symptoms of a relapse last at least 24 hours and do not occur as a result of external factors, like infection or heat.

Summary

Nearly 1 million adults in the United States live with multiple sclerosis, and around 85% to 90% have relapsing-remitting MS (RRMS). As the most common type of MS, RRMS is associated with discrete attacks of new or worsening neurological symptoms that improve or go away over time.

RRMS is typically detected in young adulthood and is more common in females. Like other forms of MS, relapsing-remitting is associated with a slightly shorter life span than the general population.