A veteran anime voice actress of Japan's beloved Doraemon robot cat is struggling with dementia, her talent agency and husband have revealed.

Despite her disease, Nobuyo Oyama, 78, remains physically healthy and eager to continue with her voice acting duties, albeit to a limited degree, Yozo Morita, head of her agency, told The Japan Times on Thursday.

Oyama's battle against the degenerative disease was initially revealed during a live radio program on Wednesday by actor Kesuke Sagawa, her husband, who reportedly said his wife "can't even remember what she had said two minutes before."

She is no longer capable of bathing and cooking without help, the actor also divulged. But Morita stressed that she has no trouble recognizing people close to her.

Oyama is best known for her stint from 1979 to 2005 as a voice actress of the globally popular "Doraemon" series.

Based on manga drawn by the late Fujiko F. Fujio, the anime features an unlikely friendship between the blue robot cat from the 22nd century and a wimpish schoolchild called Nobita.

It has aired overseas, mainly in Asia and Europe, and made its first foray into the United States last year after being reinvented for an American audience.

After finishing her role as Doraemon, Oyama suffered a stroke in 2008 and has since been left with permanent damage to the frontal lobe of her brain.

Until Oyama was diagnosed with dementia a few years ago, both the agency and her husband believed that Oyama's occasional forgetfulness was due to brain damage from the stroke, Morita said.