Stephen Hawking died on March 14, 2018, at age 76, from complications of amyotrophic lateral sclerosis (ALS). He had lived with the disease for 55 years, an almost unheard-of duration for a condition that kills most people within five years of diagnosis.
How ALS Causes Death
ALS progressively destroys the motor neurons that control voluntary muscle movement. Over time, patients lose the ability to walk, use their hands, speak, and swallow. But what ultimately kills most people with ALS is respiratory failure. The diaphragm, the main muscle responsible for breathing, weakens as motor neurons die off. Once the diaphragm can no longer do its job, the body cannot take in enough oxygen or expel enough carbon dioxide. This often shows up first during sleep, when breathing naturally becomes shallower.
Weak expiratory muscles also make it difficult to cough effectively, which means the lungs can’t clear mucus and bacteria. That raises the risk of pneumonia and other lung infections. Weakness in the throat muscles compounds the problem by allowing food or liquid to enter the airway. Together, these respiratory complications account for the majority of ALS deaths.
Hawking’s 1985 Pneumonia Crisis
Hawking’s closest brush with death before 2018 came in 1985, when he caught pneumonia while visiting CERN in Geneva. The infection was severe enough that doctors gave his wife the option of turning off life support. She refused, and Hawking underwent a tracheostomy, a surgical opening in the windpipe that helped him breathe but permanently removed his ability to speak. From that point on, he required 24-hour nursing care, funded by grants from several foundations.
Communication became painstaking. At first, the only way Hawking could form words was by raising his eyebrows when someone pointed to the correct letter on a spelling card. He later adopted the computer-based speech system that became his trademark, controlled first by a hand clicker and eventually by a cheek muscle sensor as his body continued to deteriorate.
Later Health Scares
By 2009, Hawking’s respiratory fragility was evident again. He was rushed by ambulance to Addenbrooke’s Hospital in Cambridge after becoming “very ill,” having already been unwell for several weeks with a chest infection. He had pulled out of a major science conference in Arizona shortly before. He recovered, but these episodes illustrated how precarious his condition had become. For someone with advanced ALS, even a common respiratory infection can become life-threatening because the muscles needed to cough and breathe are so compromised.
Why Hawking Survived So Long
When Hawking was diagnosed in 1963 at age 21, his doctors gave him roughly two years to live. That estimate was consistent with the median survival time for ALS patients at that time, and it remains close to average today. Most people diagnosed with ALS are over 50 and die within three to five years. Hawking outlived his prognosis by more than half a century.
Neurologists believe his extraordinary survival came down primarily to biology rather than willpower or lifestyle. His form of ALS progressed extremely slowly, sparing the non-motor parts of his brain entirely. This pattern resembles juvenile-onset ALS, a rare variant diagnosed in the teenage years that can progress over decades instead of years. Fewer than a few percent of ALS cases follow this slow trajectory, but neurologists have documented other patients diagnosed in their teens who survive into their 40s, 50s, or 60s.
Excellent medical care played a supporting role. The tracheostomy in 1985 kept him alive through a crisis that would have killed him otherwise. A feeding tube addressed the malnutrition and dehydration risks that come with difficulty swallowing. Round-the-clock nursing ensured that respiratory infections and other complications were caught and managed quickly. But specialists who studied his case emphasized that no amount of care can explain decades of survival with ALS. The disease’s biology sets the timeline, and Hawking’s biology was genuinely exceptional.
His Final Years
By the time of his death at his home in Cambridge, Hawking had been almost completely paralyzed for years, communicating through the tiny movements of a single cheek muscle. His mind, however, remained sharp. He published papers, gave lectures, and made public appearances well into his 70s. His death at 76 was not sudden or unexpected in the way a heart attack might be. It was the eventual outcome of a disease that had been slowly claiming his body for over five decades, with respiratory failure as the final mechanism, just as it is for most people with ALS.