When I was in medical school at the end of the 20th century, I was taught that Alzheimer's disease was a rare cause of dementia in middle-aged adults. The elderly had senility caused by an indecipherable mess of pathologies and aging. Now, in the 21st century, Alzheimer's is called an epidemic. It has even helped five-time nominee Julianne Moore win her first Academy Award.

In Still Alice, based on the novel of the same title, Moore portrays professor Alice Howland, who is diagnosed with Alzheimer's disease, and who suffers the relentless decay of her capacities. Reality as we know it is far more complex and nuanced. This is not the right story for our time.

During a recent visit with an 80-year-old man at the memory center where I care for patients, his wife settled into her exam room seat. Instead of opening with questions about problems or concerns she had about her husband, however, I asked what she thought of the book she carried: Still Alice.

She looked at the cover, looked back at me, and said one word: "Scary."

As a physician who studies the intersections of scientific, ethical, and social issues involving Alzheimer's, I understand the story's popularity. For older women today who fought - or at least hoped - for independence and meaningful work, the story of a 50-year-old woman losing her capacity to be herself at the peak of her career as an Ivy League college professor isn't simply a story that raises awareness. It's a horror story.

Still Alice may be praised for doing what fiction sometimes achieves - transforming a large and vexing social problem into something personal and therefore in need of national action. The best-selling book and critically acclaimed film put flesh and blood and tears into lifeless statistics about a disease that affects an estimated 5 million Americans and costs as much as $215 billion each year.

These statistics are the customary prologue for why the U.S. has a national Alzheimer's plan. But they aren't why Alzheimer's is a disease. It's a disease, a horrific disease, because of a 20th-century success story. In 1907, when a German psychiatrist named Alois Alzheimer published his case of Auguste D., a 51-year-old woman with what he titled "an unusual disease of the cerebral cortex," the patient was ruled by an emperor and could not vote, and Dr. Alzheimer did not obtain her informed consent or her husband's.

The history of the 20th century is the history of the triumph of autonomy. And Alzheimer's is a disease because it takes that freedom away. As the United States embarks on a national plan to prevent Alzheimer's, these well-intentioned - and much-needed - efforts are going to challenge the very same autonomy we wish to protect. Still Alice raises awareness, but it's not a good narrative to help us understand who has Alzheimer's disease - or how we'll live with it in the 21st century.

So, who has it?

Alice Howland's Alzheimer's is, like Auguste D.'s, an unusual disease of the cerebral cortex. She is in middle age and carries an uncommon genetic mutation that causes the afflicted to develop dementia by their fifth decade. (Auguste D. carried the same mutation). At autopsy, the brain of a patient with one of these genetic mutations routinely shows what Dr. Alzheimer described in his patient's brain: between dead neurons filled with tangles of dysfunctional tau protein are plaques of amyloid protein. It is known as "plaque and tangle pathology."

By the end of the 20th century, neuropathologists were observing that elderly patients with senile dementia had the same pattern as patients such as Alice and Auguste D. Those formerly known as senile came to be called "late-onset Alzheimer's." Alzheimer's became one great disease of plaques and tangles, and that's what I told my patients and their families.

Now I've changed my story.

Research suggests that among cognitively impaired older adults, multiple pathologies in addition to plaques and tangles aren't the exception but the norm, and yet all these combined explain just 40 percent of cognitive decline in the elderly. The results of autopsies of cognitively normal older adults further complicate the finding. A notable proportion of them have the plaque and tangle pathology of a person with dementia.

Alice Howland's Alzheimer's disease is a coherent story of a gene that leads to plaque and tangle pathology that leads to symptoms. But stories of Alzheimer's in the elderly - the imperfect relationships between pathology and symptoms, and the interactions between cognitive aging and disease - all suggest a complex disease, or even diseases. In rare cases such as Alice's, drugs may cure or at least markedly slow cognitive decline, and clinical trials are underway in these patients.

For those who live into old age, however, plaques and tangles are best thought of as risk factors such as cholesterol and blood pressure. We must be careful not to promise a cure, but, instead, a "slowing of the trajectory of cognitive decline."

How do we live with Alzheimer's?

The challenge of our success in slowing the decline will be living with cognitive impairment that, though mild, requires surveillance to ensure it's not worsening - to ensure that we're still Alice, or John, or Lisa, and so are still able to carry on with our work and daily activities.

Memory centers - clinics dedicated to the diagnosis and treatment of older adults with memory loss - won't be the only places where our autonomy will be measured and judged fit. A visit gives only a snapshot constructed out of time-intensive cognitive testing and interviews with a family member and patient. Our aging brains are inherently enmeshed in the world, offering a wealth of day-to-day data, and as we develop technologies to treat Alzheimer's, they will beget technologies to capture these data.

One of these is continuous home monitoring to track a person's daily habits in order to detect even the subtlest hints of cognitive decline, such as less use of the computer or a missed bill payment. This promises a standardized method of detection, freed of a visit to a memory center.

But it raises a challenge even more vexing than intrusions into privacy. Who decides how much change is abnormal, and, if it is, who should intervene? This question engages complex and competing interests such as when a senior residential community uses monitoring to decide whether a resident is capable of living independently or needs to surrender some autonomy and buy more expensive care.

Monitoring will reach into spaces we normally do not think of as medical. Cars can be equipped to provide real-time assessment of driving performance. A study of thousands of adults' financial transactions such as credit card balance transfers found that older adults were more likely than those in middle age to make poor financial decisions. It turns out the banking and financial-services industries are sitting on valuable data about the cognitive health of older Americans.

Monitoring our homes, driving, and finances is just one example of how - as we struggle to maintain our cognitive health and our autonomy if we want to live well and with our values intact - we ought to tackle Alzheimer's disease as not simply a medical challenge, but a public health one. A good story would help, too.

Jason Karlawish, M.D., is a professor of medicine, medical ethics, and health policy at the University of Pennsylvania and associate director of the Penn Memory Center.