Secondary Progressive MS Facts and Statistics: What You Need to Know

Secondary progressive multiple sclerosis (SPMS) is a type of multiple sclerosis that affects around 37 per 100,000 people in the United States. SPMS follows an initial relapsing-remitting phase of the disease and is characterized by steadily worsening symptoms over time.

This article will explore secondary progressive multiple sclerosis, focusing on key facts and statistics about disease prevalence, mortality rate, and more.

Secondary Progressive MS Overview

Multiple sclerosis involves the immune system malfunctioning and attacking the fatty myelin sheath surrounding nerve fibers within the brain and spinal cord. When myelin is damaged, nerve signaling is impaired, resulting in symptoms like numbness, weakness, pain, and walking problems.

Most individuals with MS are initially diagnosed with relapsing-remitting multiple sclerosis (RRMS). They experience unpredictable episodes of neurological symptoms (relapses) followed by periods of symptom improvement or recovery (remission).

Over time, many of those with RRMS eventually shift to a less inflammatory and more progressive course of the disease called secondary progressive MS.

Like other types of MS, SPMS cannot be reversed or cured. However, there are therapies to help manage the symptoms and disabilities associated with SPMS. Disease-modifying treatments can also help reduce inflammatory activity in certain people with SPMS.

How Common Is SPMS?

In 2018, the estimated prevalence of SPMS in the United States was 37.1 cases per 100,000 people, equivalent to over 120,000 individuals.

The estimated number of individuals with MS in the United States is 363 cases per 100,000 people. This has increased from 309 cases per 100,000 people in 2010.

SPMS by Race and Ethnicity

MS, including SPMS, affects most racial and ethnic groups. While past studies indicate that MS is most common among White people, there is evidence to suggest that MS prevalence has been similar among Black and White people for decades.

Specifically, one study in Southern California reported the MS prevalence to be 226 Black cases and 238 White cases per 100,000 people. MS prevalence remains significantly lower among Hispanics and Asians.

In terms of specific racial differences in disease, there is research suggesting that compared to White people with MS, Black people are at a higher risk for early disability and a worse prognosis (disease outcome).

It's unclear whether this finding is because Black people experience a naturally more aggressive MS course or if certain environmental or social factors are involved.

SPMS by Age and Gender

There is a wide variation in timing from the first symptom of RRMS to the onset of SPMS. Research has found the median time to be approximately 20 years in untreated people, typically around mid-life or 40 to 55.

Regarding sex differences, SPMS is more common in females than males. That said, males have a worse outlook, as they experience neurologic disabilities faster than females. Males with RRMS are also more likely to transition to SPMS than females.

Causes of SPMS and Risk Factors

Experts suspect the cause of secondary progressive multiple sclerosis involves a unique interplay of various environmental and genetic factors.

Environmental factors explicitly linked to the development of RRMS (the phase before SPMS) include:

• Vitamin D deficiency
• Smoking
• Prior infection with Epstein-Barr virus
• Obesity in early childhood

Keep in mind that the transition from RRMS to SPMS is often subtle and can be challenging to pinpoint. People often experience slowly worsening symptoms and changes in function, with or without relapses and periods of symptom stability.

In addition to a shift in symptom manifestation, research suggests that a change in disease pathology occurs when moving from RRMS to SPMS. Specifically, this change involves shifting from an inflammatory process to one of neurodegeneration (dying of nerve cells).

While it's impossible to predict when (or if) individuals with RRMS will advance to SPMS, factors that increase their chances include:

• Older age at MS onset
• Male sex
• Experiencing frequent relapses early on in the disease
• Longer disease duration
• Increased baseline Expanded Disability Status Scale (EDSS) score (used to measure MS severity and progression)
• Higher early increase in EDSS score
• Higher lesion (areas of inflammation) burden as seen on magnetic resonance imaging (MRI)
• Spinal cord involvement
• Lower brain volume as seen on MRI
  

What Are the Mortality Rates for SPMS?

People with MS, including those with SPMS, have a nearly three times greater risk of death than the general population.  

Despite this higher mortality rate, MS is not considered fatal. While some people with MS ultimately succumb to a complication related to the disease, like a lung or urinary tract infection, many others die from the same causes as those in the general population (e.g., cancer or heart disease).

Moreover, even though MS is currently associated with a seven-year shorter lifespan compared to the general population, emerging research suggests that life expectancy is increasing due to various disease-modifying therapies.

Scientific evidence suggests that approximately 90% of people diagnosed with MS in their 20s may live into their 70s.

Ultimately, it's essential to understand that MS is just one factor affecting a person's longevity. Other factors, like genetic makeup, lifestyle habits (e.g., smoking and nutrition), and other medical conditions like diabetes, influence lifespan.

Screening and Early Detection

There is no screening or single diagnostic test for SPMS. Instead, SPMS is detected by a neurologist (a physician specializing in diseases of the nervous system) after a person has experienced RRMS.

Various diagnostic strategies or tools often include:

• A medical history documenting a change in symptoms 
• A neurological exam
• MRI scans of the brain and spinal cord

Generally speaking, people with SPMS report worse physical functioning and rate their MS as more severe than those with RRMS.

In addition, people with SPMS are more likely to experience the following symptoms compared to those with RRMS:

• Problems balancing or walking
• Muscle spasms and stiffness
• Bladder dysfunction
• Constipation
• Sexual problems
• Tremor (uncontrollable shaking)

Summary

Around 85% of those living with multiple sclerosis (MS) are initially diagnosed with relapsing-remitting MS (RRMS). Many eventually shift to a progressive form of the disease called secondary progressive MS (SPMS), where their symptoms slowly worsen or increase over time.

SPMS occurs across most ethnic groups and is more common in females than males. Like other types of MS, SPMS is associated with a slightly shorter lifespan, although this may change with the advent of disease-modifying therapies.