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Comedian Robin Williams' widow says Lewy body dementia killed her husband

1.4 million Americans suffer from Lewy body dementia

LBD shares common symptoms with Alzheimer's and Parkinson's diseases

CNN  — 

Comedian Robin Williams’ widow, Susan Williams, said she and her husband “were living a nightmare” in the months leading up to his death.

“My best friend was sinking,” an emotional Williams told ABC’s Amy Robach in an interview that aired Tuesday, her first since Robin Williams killed himself in August 2014.

Williams said she’s spent the last year trying to get to the bottom of what led him to take his own life. Contrary to what most people think, she said, it wasn’t depression, nor was it a re-emergence of his longtime struggles with alcohol and drug addiction.

Robin Williams had no alcohol or illegal drugs in his system; he’d been sober for eight years, his wife said.

What drove her husband to suicide, “was what was going on in his brain,” Williams said.

“The chemical warfare that no one knew about.”

‘Chemical warfare’

That “chemical warfare” that doctors conducting Robin Williams’ autopsy discovered was Lewy body dementia.

Though not nearly as well known (or talked about) as Alzheimer’s disease, which accounts for more than half of dementia diagnoses in the United States, Lewy body dementia, or LBD, is the second most common type of progressive dementia.

Nearly 1.4 million Americans are known to have the disease, but because it’s a relatively “young disorder,” Angela Taylor, director of programming for the Lewy Body Dementia Association said, that number is likely much higher.

LBD is caused when normal proteins in the brain begin to aggregate, forming clumps called Lewy bodies that, as they spread, “muck up the ability for the brain to transmit signals,” said Cleveland Clinic neurologist Dr. James Leverenz.

Robin Williams: Full of demons, full of heart

Like Alzheimer’s disease, symptoms of LBD include cognitive problems like confusion, reduced attention span, and memory loss, Taylor said.

But LBD also affects a patient’s movements, as well as their mood, making it a “triple threat,” Taylor said.