On Wednesday, the family of actor Bruce Willis announced that he would take a step back from acting in response to a diagnosis with aphasia, a condition that affects the ability to perceive and produce communication. In an Instagram post shared by several of Willis’ family members, they wrote that after much consideration, the diagnosis would halt Willis’ acting work, and that the decision was conclusive enough to bring the public into the fold. “We are moving through this as a strong family unit,” reads the caption, co-signed by Emma Willis and Bruce’s children, along with his ex-wife Demi Moore and their three children. “[W]e know how much he means to you, as you do to him.”

It’s striking to see someone who spent decades as the prototypical action hero, whose job usually involves overcoming A-list villains against seemingly insurmountable odds, susceptible to ordinary human frailty. Even the post announcing Willis’ condition showcases his formidability: a picture of him coyly eyeing the camera in a bathrobe. 

Undeniably, Bruce Willis’ condition is something serious. Aphasia is a communications disorder that disrupts one's ability to understand or produce speech—and sometimes also reading or writing. According to Johns Hopkins Medicine, aphasia may leave someone straining to produce comprehensible sentences, with even short phrases requiring serious effort. In other cases, someone may “speak in long confusing sentences, add unnecessary words, or create new words.” That would upend anyone’s life; for an actor, doubly so.

The cause of aphasia varies. A stroke or an injury causing the brain to hemorrhage can lead to the condition’s appearance, but aphasia doesn't always come from a traumatic event. “It can also occur after a tumor,”  Dr. Swathi Kiran, director of the Aphasia Research Laboratory at Boston University, told GQ. “In some cases, aphasia can also be progressive in nature, in that it worsens over time. And that condition is called primary progressive aphasia.” The Instagram post announcing Willis’ aphasia didn’t specify which diagnosis he’d received.

The announcement did specify that the aphasia “is impacting [Willis’s] cognitive abilities,” something that has been noticed on sets in recent years. Dr. Kiran said cognitive impairment was seen specifically in cases of primary progressive aphasia. When caused by a specific event, like a stroke, aphasia strictly strikes communication abilities—not thinking abilities. 

While aphasia lacks the name recognition of, say, cancer, Dr. Kiran points out that it is pretty widespread: Two million people in the United States have it, and one in three strokes lead to aphasia. What’s more, aphasia is a life-long diagnosis.

But even more than its prevalence and permanence, Dr. Kiran stresses that aphasia is treatable. It may be an unfortunate condition to face, but “traditional speech and language therapy exercises that are done regularly and repeatedly can improve the brain’s function.” And those therapies can actually be pretty effective. “People who do a lot of therapy—especially if they receive the therapy early after their diagnosis—can recover and go back to their jobs,” she said. “Even when the condition is progressive, like in primary progressive aphasia, recent research shows that rehabilitation can stall or slow down the decline.”

Because aphasia is so widespread, it’s also closely studied, leading to a new generation of treatment options beyond the conventional suite of therapies. Currently, studies on mitigating aphasia by sending electrical currents through the brain are underway. That treatment is still a long way off from widespread use. “But, I think the results are promising,” she said. 

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