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Why Most Alzheimer’s Research Is Done On Early-Onset Patients Like Pat Summitt

When former Tennessee women’s basketball coach Pat Summitt died Tuesday morning, news outlets, including ESPN, reported the cause of her death as “early-onset dementia, Alzheimer’s type.” That’s more than just a long-winded way of saying “Alzheimer’s.” By using five words instead of one, journalists were trying to point a big, flashing neon arrow at the complex realities of dementia.

Dementia is more of a symptom than a diagnosis, and it can be caused by a number of different diseases. Even Alzheimer’s, the most common type of dementia, doesn’t seem to have a single cause. Instead, what ties Summitt to millions of other Alzheimer’s patients all over the world is the physical damage it wrought in her brain.

Worldwide, 47.5 million people are living with some kind of dementia. Alzheimer’s represents 60 percent to 70 percent of those cases. Imagine a map of a city — roads branching out, intersecting with other roads, creating a network that allows mail to be delivered, food to be sold and brought home, people to get to their jobs. What would happen to that town if random intersections were suddenly barricaded and impassible? That’s the dystopian chaos Alzheimer’s causes, as damaged proteins clog the neurons and inhibit the flow of information from one neuron to another. Cut off from food, as well as data, the cells die. The brain shrinks. Eventually, the person dies, too. Afterward, doctors can cut into their brain and see the barriers, which are called plaques.

Today, doctors can diagnose Alzheimer’s in a living patient with greater than 90 percent accuracy, through a combination of cognitive tests and brain scans that rule out other kinds of dementia. But the final proof is in the pathology. Physical damage can have many different causes — from genetics to traumatic brain injury. There might even be links to cardiovascular health, said Dean Hartley, director of science initiatives at the Alzheimer’s Association. Likewise, Alzheimer’s doesn’t look the same in every patient.

Summitt was first diagnosed, at the age of 59, after suffering from memory lapses — par for the course with any dementia. But other people first notice something is amiss when they have problems with their vision, become depressed and reclusive, or when decision-making abilities desert them. Summitt experienced that latter issue. In her memoir, “Sum It Up,” she wrote about finding herself suddenly unable to follow the action in a game or plan her players’ next move.

In some ways, Alzheimer’s is a bit like cancer. During the past few decades, scientists have come to think of the big C as more like a whole alphabet of diseases. Although Alzheimer’s is still just one thing, said Eric McDade, assistant professor of neurology at Washington University School of Medicine, it is useful to think of it as a single destination that can be reached by many roads. “As a physician, we often say, ‘if you’ve seen one person with Alzheimer’s, you’ve seen one person with Alzheimer’s,” he told me.

So how do you treat such a varied disease? And how do you spot it before it begins to take a major toll? This is where people who share Summitt’s early-onset diagnosis become important. Although 5.4 million Americans have Alzheimer’s, only about 200,000 of those are diagnosed before age 65. Summitt was 64 when she died. But this small cadre is the group most-studied by scientists.

These people are special because their Alzheimer’s is more likely to have a strong genetic component than the kind that strikes in old age. Among their number are a sub-subset of people whose Alzheimer’s is dominantly inherited. People with these genes make up about 1 percent of Alzheimer’s patients worldwide. They will definitely get Alzheimer’s, they’ll get it early, and they have a 50 percent chance of passing it on to their children.

Their personal tragedy is also a scientific opportunity. Dominantly inherited Alzheimer’s patients are the only people who can be diagnosed with Alzheimer’s via genetic test, long before any plaques form or symptoms appear. That means they’re our best opportunity to study how the disease works, what other kinds of changes it makes to the body, and what treatments might actually slow or stop its progression. And, because Alzheimer’s is many roads leading to the same, grim place, what scientists learn about them should be applicable to the broader population of patients.

McDade is the associate director of the Dominantly Inherited Alzheimer Network, an international project that tracks people who carry dominant alzheimer’s genes and connects them with clinical trials. Started in 2009, DIAN will run until 2019. In the end, they hope to come away with information that will lead to improved diagnostic tests, better treatments, and a deeper understanding of how the disease that took Pat Summitt’s life really works.

CORRECTION (July 5, 11:38 a.m.): An earlier version of this article misstated the name of Pat Summitt’s memoir. It is “Sum It Up,” not “Game On.”

Maggie Koerth-Baker is a senior science writer for FiveThirtyEight.

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