Dubbed the "Iron Lady," Britain's hard-nosed former Prime Minister Margaret Thatcher was revered for her nimble command of world events and her quick verbal repartee.
But today, in a soon-to-be-published memoir, her daughter Carol describes an 82-year-old woman -- the world leader once feared and admired -- as humbled by memory lapses so severe she doesn't even know that her longtime husband has died.
Readers across Britain called the publication of details of Thatcher's decline "exploitive" and "opportunistic." But reaction to the memoir also underscores the shame many feel about the consequences of dementia especially when it strikes the most intellectually powerful.
"It's obviously a tragedy," said Ronald Reagan Jr., whose political father suffered for many years from the most common form of dementia -- Alzheimer's disease -- before his death in 2004. "But the idea of going into details of [Thatcher's] dementia are in monumentally bad taste and unnecessary."
"I suspect there is still a vestige of that in the disease's nature," Reagan told ABCNews.com. "It affects the brain and becomes a mental illness in a way."
Dementia -- a Latin word for "irrationality" -- is an umbrella term for more than 100 diseases that affect the brain in old age, according to the National Institutes for Health. An estimated 2 million to 4 million Americans have some form of the disease.
Perhaps the most highly publicized case was that of former President Reagan -- Thatcher's conservative political soul mate. He went public with his diagnosis in a televised statement in 1994, a decade before he died of the disease.
Other powerful figures who suffered from dementia were Hollywood icon and Reagan friend Charlton Heston, as well as 1964 Republican presidential contender Barry Goldwater and professional boxer Sugar Ray Robinson.
"Ronnie's long journey has finally taken him to a distant place where I can no longer reach him," said Reagan's wife, Nancy, just a month before he died in 2004. "Because of this I'm determined to do whatever I can to save other families from this pain."
In the case of Thatcher, she suffered several mild strokes before doctors advised her against public speaking in 2002. In March she was admitted to a hospital for tests after she felt ill during a House of Lords dinner.
Serving as prime minister from 1979 to 1990, she had been an intellectual powerhouse, reportedly sleeping just four hours a night. Her daughter Carol Thatcher, a television personality, said she first noticed her mother's memory problems in 2000.
In her memoir, "A Swim-On Part in the Goldfish Bowl," which will be published next month, her daughter describes Thatcher's inability to remember world affairs or even the 2003 death of her husband, Denis.
"I had to keep giving her the bad news over and over again," the younger Thatcher writes. "Every time it finally sank in that she had lost her husband of more than 50 years, she'd look at me sadly and say 'Oh' as I struggled to compose myself. 'Were we all there?' she'd ask softly."
Most people remain "alert and able" as they age, but after age 65, the risk for dementia rises quickly, according to the NIH. Two percent of all Americans suffer from dementia before the age of 69, but by age 80, the risk increases to 20 percent. At 90, one-third of all people have some form of dementia.