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Spinal Muscular Atrophy Life Expectancy: What’s Known and What’s Unknown?

Posted on April 07, 2022
Medically reviewed by
Evelyn O. Berman, M.D.
Article written by
Eli Sachse, RN

Medical treatments have dramatically changed the prognosis (outlook) for people living with spinal muscular atrophy (SMA). Between new treatments and improved nutritional and respiratory care, there is reason to hope for increased life spans, especially for those with severe forms of the disease.

The outlook for people with SMA is rapidly improving. Still, it’s difficult to predict how the disease will progress and impact life expectancy and physical ability.

Classifying SMA Severity and Types

The term “motor milestone” generally refers to achievements or setbacks in physical abilities. Doctors can use motor milestones to define or classify diseases. For example, SMA types (type 1, type 2, etc.) were traditionally classified based on motor milestones like sitting independently, standing, or walking.

As medical treatments continue to advance, people with SMA are beginning to defy these traditional classifications. They are living longer, achieving more motor milestones, and maintaining their abilities. This has led some scientists to suggest that SMA types be seen as more of a continuum than distinct groups.

As the lines between SMA types begin to blur, doctors can find it harder to estimate a person’s abilities or life expectancy. This is especially true for the more severe types of SMA.

Life Expectancy

Estimations of life expectancy are always educated guesses. SMA specialists with decades of experience can make mistakes. Even before SMA treatments were available, researchers noted that the disease progressed differently in people with the same type of SMA. This makes outcomes for some nearly impossible to predict.

One mySMAteam member shared their experience: “I was diagnosed with SMA type 1 when I was 6 months old. The doctors told my parents that I wasn’t supposed to live to see my first birthday, but now I’m 26 years old and living my life to the fullest!”

SMA Types 0 and 1 (Werdnig-Hoffmann Disease, or Infantile-Onset SMA)

SMA type 0 is often grouped with type 1. It is the most severe type of SMA, with onset happening before birth. Doctors used to believe that children with SMA type 0 would not live past the age of 6 months, on average. However, starting drug therapies in the first few months of life can help shift the prognosis for these early forms of SMA.

The average life expectancy for children with SMA type 1 used to be less than 2 years. However, drug therapies are helping children with infantile-onset SMA achieve motor milestones that were previously considered impossible. Some children have even learned to walk. These exciting advances mean that outcomes for those with severe types of SMA can be difficult to predict. However, it is clear that both quality and length of life for those with infantile-onset SMA are improving with treatment.

SMA Type 2 (Dubowitz Syndrome)

Life expectancy and motor milestones for those with SMA type 2 vary — and are nearly impossible to predict. For example, people with SMA type 2 may or may not be able to sit or walk. They can have life spans that are shortened, or they can live into adulthood.

Drug therapy and better respiratory and nutritional support can improve motor function in people with SMA type 2. Before SMA treatment, it was commonly accepted that people with SMA type 2 would pass in their 30s. However, with drug therapy extending the life span of those with SMA type 1, future studies may show longer average life spans for those with SMA types 2, 3, and 4 as well.

SMA Types 3 and 4 (Kugelberg-Welander Disease and Adult-Onset SMA)

Before SMA treatments became available, SMA types 3 and 4 were not considered to shorten life spans. People with SMA types 3 and 4 can expect to live lives as long as others in the general population.

Discussing End-of-Life Preferences

No matter your SMA diagnosis, age, overall health, and prognosis, it’s worthwhile to have conversations about end-of-life care. The lifestyle and quality of life you want — as well as your preferences around end-of-life care and how you want to be remembered — are important. While it may be difficult to have those conversations, they can leave everyone with peace of mind knowing that they understand what you want.

Key preferences to discuss include:

  • Whether to use a breathing or feeding tube
  • When to withdraw life-supporting treatment
  • Wishes after passing

One way to start this conversation is to ask your primary health care provider about creating an advance directive. Sometimes, a nurse can guide you through the process. Some people also designate someone they trust as their medical power of attorney. When you make someone your medical power of attorney, they can make medical decisions on your behalf if you become incapacitated.

Early Screening and Treatment Are Crucial

Most states now mandate SMA testing for newborns. Early testing leads to early diagnoses for more children — and the sooner that treatment begins, the better the outcome.

Babies diagnosed with SMA today may have very different futures compared with those diagnosed even a decade ago. Treatments are already saving and improving lives.

Talk With Others Who Understand

On mySMAteam, the social network for people with SMA and their loved ones, more than 1,500 members come together to ask questions, give advice, and share their stories with others who understand life with SMA.

Do the unknowns around SMA and life span give you hope, or add to anxiety? How do you cope with uncertainty? Share your experience in the comments below, or start a conversation by posting on your Activities page.

All updates must be accompanied by text or a picture.
Evelyn O. Berman, M.D. is a neurology and pediatric specialist and treats disorders of the brain in children. Review provided by VeriMed Healthcare Network. Learn more about her here.
Eli Sachse, RN is a registered nurse living in California. He has written about health topics for Sonoma Medicine and Microcosm Publishing. Learn more about him here.

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