Some of the most important studies of potential treatments for Alzheimer's disease rely on a group of participants who know they may never fully reap the benefits.
"It's not for us," says June Ward, 64, who carries a rare gene mutation that virtually guarantees she will get Alzheimer's in the next few years. "It's for my sister's children and their children, so that they won't have the same 'nothing' to choose from."
Ward is a member of the Dominantly Inherited Alzheimer Network (DIAN), which includes more than 200 families at more than 40 sites in 18 countries. All the families who carry gene mutations that cause symptoms of Alzheimer's to appear in middle age, or even earlier.
The families' willingness to serve as research subjects over the past two decades has allowed scientists to make key discoveries about how Alzheimer's begins, and how certain drugs may slow its progress.
Yet DIAN, run by WashU Medicine in St. Louis, faces an uncertain future amid cuts and delays in federal funding. It is currently maintaining only essential functions while awaiting word on critical grants from the National Institutes of Health, or NIH.
"The network that's been built up, the years that have gone into the training and the relationships — without funding, all of that would fall apart," says Dr. Tammie Benzinger, a professor of radiology at WashU who oversees brain imaging of DIAN participants.
Families riddled with dementia
DIAN is made up of families like Ward's.
These families carry one of three different gene mutations that can cause Alzheimer's symptoms to appear in a person's 40s or 50s.
Each child born to a parent with the mutation has a 50-50 chance of inheriting it. People who inherit the mutation are all but certain to develop Alzheimer's before turning 65.
The high risk in these families makes them highly valued participants in Alzheimer's research studies, says Dr. Randall Bateman, a professor of neurology at WashU Medicine and co-director of DIAN.
They represent "the only population in the world where we not only have certainty about whether they will get it, but when they will get it," he says.
Bateman began studying affected families in the early 2000s. He was trying to understand what causes the protein amyloid to appear in the brains of people with Alzheimer's.
"It was clear to me that people with these mutations could answer that question," he says.
But the mutations are so rare that no single research center had enough family members for a large study. So in 2008, the NIH began funding DIAN to create an international registry.
A window on Alzheimer's
The multimillion-dollar investment has paid off, Bateman says. For example, brain scans of DIAN family members helped scientists discover how Alzheimer's begins.
"Before the first memory loss is noticed, there is this 20-year period where changes are occurring in the brain," Bateman says.
In 2012, DIAN teamed up with the Alzheimer's Association and pharmaceutical companies to create its clinical trials unit, called DIAN-TU.
Early trials of DIAN families showed that certain drugs could reduce the sticky amyloid plaques that are associated with Alzheimer's. A study in 2025 suggested that reducing amyloid very early in the disease could delay symptoms in people with a mutation.
Scientists have also discovered through DIAN that, very rarely, a person will inherit a mutation that usually means they are certain to develop Alzheimer's, and yet somehow they do not develop the disease. If researchers can figure out why these individuals are protected, it might lead to treatments for other people at high risk of Alzheimer's.
By serving as a test group for experimental amyloid drugs, DIAN families helped pave the way for lecanemab and donanemab, the two amyloid drugs now on the market. More recently, the DIAN network has helped researchers assess the drugs' side effects, which include swelling and bleeding in the brain.
"What we've seen with the amyloid therapies is how important this DIAN cohort is," Benzinger says.
A diagnosis, then a career
Many DIAN family members do more than volunteer for research studies.
Take Lindsay, who asked that we use only her first name in order to frankly discuss her family's medical history.
Lindsay's father was diagnosed with Alzheimer's when he was 48 and she was 18.
Lindsay's response was to immerse herself in brain science.
"I went to our local library and I checked out every single book on Alzheimer's disease," she says. "I was like, there's got to be something we can do."
There wasn't. So in college, Lindsay focused on science courses. Then she joined DIAN, even though that meant several days of uncomfortable tests.
"I got a lumbar puncture, I got an MRI scan, I got a PET scan, lots and lots of blood collected from me," she says. She also got a genetic test, but chose not to see the result until years later.
Eventually, Lindsay learned that she does not carry the early Alzheimer's mutation. Yet she continues to attend the annual meeting of DIAN families, and to help run a nonprofit for those families called Youngtimers.
She also holds a Ph.D. in neuroscience and works in an Alzheimer's disease lab at a major university.
An uncertain future
But like many members of DIAN, Lindsay is concerned about the network's funding, which has come largely from the NIH's National Institute on Aging.
When the second Trump administration began in 2025, DIAN's leaders were in the process of renewing the project's main grant. The new administration was looking to slash research funding, especially money that supported international projects like DIAN.
The grant renewal would have provided $13 million in its first year. But federal officials rejected the application.
That prompted Lindsay and other family members to draft a petition urging the NIH to reconsider. "We got 600 signatures in three days," Lindsay says.
Ultimately, NIH offered about $8 million in bridge funding for the year instead of the $13 million DIAN applied for.
The government also ended all funding that had gone to DIAN's international sites. Those sites are being sustained, temporarily, with funding from the Alzheimer's Association.
DIAN's future remains in doubt even though Congress, in February, approved a $100 million increase in funding to the NIH for Alzheimer's and dementia research. The president signed the bill.
But grant reviews continue to lag at the NIH amid government shutdowns and numerous changes in scientific leadership.
A review DIAN expected in January or February has been pushed to May, just weeks before the group's bridge funding is scheduled to end.
Despite all this, Lindsay says she's trying to remain optimistic.
"I'm still that naive 18-year-old girl thinking that she can cure her dad," she says.
And on the scientific front, there are hopeful signs, she says, especially research suggesting amyloid drugs can delay Alzheimer's in DIAN participants who carry the mutation.
"I 100% believe that the first Alzheimer's survivor will be from this community," she says.
But only if the community continues to exist.
Copyright 2026 NPR
