Ady Barkan, a well-known activist who campaigned for Medicare for all while struggling with the neurodegenerative disease A.L.S., died on Wednesday in Santa Barbara, Calif. He was 39.

His death, at Santa Barbara Cottage Hospital, was announced by Be a Hero, the political organization he co-founded in 2018.

Mr. Barkan was diagnosed with A.L.S., or amyotrophic lateral sclerosis, in 2016, four months after the birth of his son, Carl. The disease, which causes paralysis, strikes many patients in the prime of life and often leads to death within two to five years.

As Mr. Barkan confronted his mortality, he dedicated the rest of his life to changing the American health care system.

His profile and influence grew even as his health deteriorated, in part because he had a knack for blending his personal story with calls to action. He testified before Congress, interviewed Democratic presidential candidates and spoke at the Democratic National Convention.

“That’s the paradox of my situation,” he told The New York Times in 2019. “As my voice has gotten weaker, more people have heard my message. As I lost the ability to walk, more people have followed in my footsteps.”

Ady Barkan, a progressive activist who became a champion for single-payer health care after receiving a diagnosis of A.L.S. in 2016, spoke at the Democratic National Convention.

Hello, America. My name is Ady Barkan, and I am speaking to you through this computer voice because I have been paralyzed by a mysterious illness called A.L.S. Like so many of you, I have experienced the ways our health care system is fundamentally broken: enormous costs, denied claims, dehumanizing treatment when we are most in need. Since my shocking diagnosis, I have traveled the country meeting countless patients like me, demanding more of our representatives in our democracy. Today we are witnessing the tragic consequences of our failing health care system. In the midst of a pandemic, nearly 100 million Americans do not have sufficient health insurance, and even good insurance does not cover essential needs like long term care. Our loved ones are dying in unsafe nursing homes, our nurses are overwhelmed and unprotected, and our essential workers are treated as dispensable. We live in the richest country in history, and yet we do not guarantee this most basic human right. Everyone living in America should get the health care they need, regardless of their employment status or ability to pay. Even during this terrible crisis, Donald Trump and Republican politicians are trying to take away millions of people’s health insurance. With the existential threat of another four years of this president, we all have a profound obligation to act — not only to vote, but to make sure that our friends, family and neighbors vote as well. We must elect Joe Biden. Each of us must be a hero for our communities, for our country. And then, with a compassionate and intelligent president, we must act together and put on his desk a bill that guarantees us all the health care we deserve.