Bruce Willis is stepping away from acting after recently being diagnosed with aphasia, a condition that is “impacting his cognitive abilities,” according to a statement shared by his family.

Aphasia, which can cause varying degrees of impairment in speech or understanding language, currently affects more than 2 million Americans, the National Aphasia Association estimates.

The condition often results from a stroke or brain injury, but can develop over time due to brain tumors or progressive neurological disease.

Aphasia can affect people of any age, though most who are diagnosed are “middle-aged or older,” according to the National Institute of Health.

There are several different types of aphasia that fall within two categories: fluent and nonfluent.

Fluent aphasia generally develops from damage to the temporal lobe, and can result in a common form of the condition called Wernicke’s aphasia, which may cause a person to have trouble understanding speech, or speak in “long, complete sentences that have no meaning,” the NIH writes.

Nonfluent aphasia, found more commonly in those with damage to the frontal lobe, can result in Broca’s aphasia, a type that may hinder speech and cause a person to speak in short phrases or smaller words, despite generally having a better understanding of speech.

Nearly all patients with aphasia have word-finding difficulties – that is, coming up with the correct name of persons, places, things, or events,” the Cleveland Clinic notes.

Patients who suffer aphasia as a result of a brain injury may recover some of their language and cognitive abilities on their own, though many may not.

Rehabilitation programs focusing on speech and language therapy can offer further help. Drug therapies are also being explored as an “experimental approach” to treatment, according to the NIH.