Former presidential aide Omarosa Manigault Newman’s newly published book Unhinged, about her 15-year relationship with Donald Trump, traces a familiar narrative arc for a political insider’s tell-all: She settles scores, defends her own actions, and describes the evolution of her relationship with the US president.

Disturbingly, she also argues that Trump is suffering a dramatic mental decline, from the quick-thinking Apprentice host to a lonely, befuddled president who rattles around in the White House with rage and confusion.

White House press secretary Sarah Sanders has dismissed the book, out today, as “riddled with lies and false accusations” by a disgruntled former employee. This morning, Trump himself called Omarosa a “dog” on Twitter.

Omarosa’s doubts about Trump’s mental acuity are not the first. The president’s repetitive speaking patterns, apparent difficulty retaining new information, and reliance on notes in public speeches have raised questions before. In January, White House doctor Ronny Jackson said he had no concerns about Trump’s cognitive ability or neurological function. Jackson is no longer the president’s physician after allegations of improper conduct on the job.

Trump, at age 72, is the oldest president ever at the time of his first term (Ronald Reagan was elected to a second term at age 73). He also has a family history of Alzheimer’s; his father Fred was diagnosed with the disease at age 87, and died six years later after catching pneumonia. Family history and heredity are the most important factors for determining whether you will get the disease, the Alzheimer’s Association says.

Omarosa’s account paints a vivid contrast between the Trump of the early 2000s and the president today. About taping the first season of The Apprentice in 2003, she writes:

Five hours is a long time. Everyone lagged, except for one person—Trump himself. His energy was high and his focus sharp. He engaged on an elevated level and had a full grasp of the rules and parameters of each task. He knew each of our names and performance histories, show by show. He spoke with a wide-ranging vocabulary, made eye contact, and sat still. He analyzed our performance and arguments on the fly. He kept all these balls in the air at the same time, without any sign of fatigue or stress.

She recalls him dismissing one candidate on the first season of The Apprentice after they failed to calculate their profits and losses properly, recalling:

Trump repeated a lengthy numbers sequence with no notes in front of him, calculated them in his head in moments, and came to his conclusion that the math-addled contestant should be fired.

The Trump of 2005 would have sought counsel and advice, Omarosa writes, instead of responding impulsively on Twitter to a phone call or revelation on TV. “Back then, he could process complex information, differences of opinion, and weigh the consequences,” she said.

Trump’s memory is failing, Omarosa alleges, to the point that he doesn’t recognize new hires when they come into the Oval Office. “Any time somebody new came in to brief him, he’d get angry and say, ‘Who’s that guy? What’s he want?’”

He’s “paranoid and irritable,” she writes, and “anything could trigger fits of rage.” Close advisors were subject to long, rambling phone calls, and subject to screaming tirades if they didn’t deliver what he wanted.

As she watched his interview with NBC’s Lester Holt about the firing of FBI director James Comey, she thought:

I’d known Donald to exaggerate and boast. He’d told white lies and lies of omission, ignorance, or misunderstanding. He’d bent the truth purposefully to make himself look good. But this was different. It was like he didn’t know what the truth was or couldn’t remember what he’d previously stated as truth.

His “mental decline could not be denied,” Omarosa writes, a fact that she believes she recognizes more than others in the White House because she knew him longer.

Trump’s sister Lara refused to discuss the issue, as did other “high level people in the White House,” Omarosa claims. The former presidential advisor even slipped a Boston University study about the correlation between daily diet-soda consumption and dementia into Trump’s “to read” file, but it was removed before he saw it by former aide Rob Porter.