How Did Stephen Hawking Survive ALS For So Many Years? It's a Medical Mystery

Until his death, theoretical physicist Stephen Hawking was perhaps the most famous person with amyotrophic lateral sclerosis (ALS), a progressive neurodegenerative condition often known as Lou Gehrig's disease for the other celebrity to receive the diagnosis.

Unlike Hawking, baseball player Gehrig survived just two years after the diagnosis, and the unusual manifestation of the physicist's condition is part of what made his case so famous. Hawking was diagnosed with ALS in 1963 at age 21. That's much younger than the typical age of diagnosis, which is around 55. The average life expectancy for the condition is a little more than a year—but instead, he lived half a century longer.

ALS is a type of motor neuron disease in which the cells that link the brain to the body, controlling movement, die. That includes the muscles that control breathing, which is why many people with ALS die of respiratory failure. (The loss of muscles used to swallow are another prominent challenge for those with the disease.)

Even with a serious disease like ALS, a handful of patients always survive longer than their life expectancy at diagnosis, and there's some evidence that the juvenile-onset form of the disease progresses more slowly. But Hawking's case was widely considered exceptional. "He's certainly an outlier," neurologist Leo McCluskey of the University of Pennsylvania told Scientific American in 2012.

As the years passed and Hawking continued to beat the odds, both he and his doctors were always stumped about how he survived so long. Typically, the patients who do survive long after a diagnosis use ventilators, which Hawking did not. (He did lose his voice after he caught pneumonia and needed an operation to restore his breathing.)

Related: What is amyotrophic lateral sclerosis? Stephen Hawking's disease explained

Hawking credited his excellent medical care—and his accommodating career as a theoretical physicist—for giving him an edge. Doctors have also speculated that his particular genetics may have helped him survive for longer.

All doctors can do for patients with ALS is treat the symptoms and support the person's lifestyle. There is no cure for the disease.