Comedian Robin Williams had health problems that would have killed him within three years if he had not ended his own life, his widow has said.

In her first interview since the actor died last August, Susan Williams said her husband was "disintegrating before my eyes" in the weeks before his death.

"We were living a nightmare," she told Amy Robach from ABC's Good Morning America.

He had been diagnosed with Parkinson's disease and had signs of a condition known as dementia with Lewy bodies.