It’s highly likely that if you’re reading this, you know someone affected by Alzheimer’s dementia. In fact, one in 10 people over 65 years old lives with the condition. It is also the sixth leading cause of death in the United States, as well as a leading cause of poor health among those in their elderly years—especially people of color, who are more likely than white people to develop Alzheimer’s or other dementias.
Early diagnosis is a crucial tool to help slow progression of memory loss in older adults. However, Alzheimer’s is challenging to diagnose, due in part to the lack of obvious medical markers to distinguish it from other forms of dementia. “Currently, Alzheimer’s dementia is diagnosed in the doctor’s office, typically using cognitive testing,” explains Rebecca Edelmayer, Ph.D., director of Scientific Engagement for the Alzheimer's Association in Chicago. The disease can only be diagnosed with certainty after death upon examination of brain tissue.
That’s why a new Alzheimer’s diagnostic blood test is making waves in the medical community. A study published in JAMA looked at a blood biomarker called plasma phospho-tau217 with the ability to pinpoint Alzheimer’s decades before symptoms appear. Experts say this could represent a breakthrough in the fight against Alzheimer’s worldwide. “We need those tools and technologies to help diagnose individuals at the earliest stages of their disease,” Edelmayer says, paving the way for better prevention moving forward.
What Makes This Test So Useful?
Here’s the thing about Alzheimer’s detection: it is typically a diagnosis of exclusion, meaning your doctor will rule out other conditions before deciding you likely have Alzheimer’s dementia.
Edelmayer explains that usually someone will come in with concerns about themselves or a family member, based on symptoms of memory loss they’ve been noticing. The doctor will conduct a series of blood and urine tests, a cognitive questionnaire involving friends and family, and brain scans to rule out things like stroke, brain tumor, Parkinson’s disease, or sleep issues.
Alzheimer’s isn’t the only form of dementia someone can develop. There’s also vascular dementia, frontotemporal dementia, and dementia caused by specific medical conditions like Huntington’s disease, a head injury, mental health issues, HIV complications, and more. The treatment protocol will depend on what type of dementia the person has. For Alzheimer’s, there is no known cure, but there are medications that help preserve memory as well as lifestyle changes that can make a person more alert and comfortable as the disease progresses.
This new blood test can detect Alzheimer’s through a very specific mechanism: a protein called tau that accumulates in the brain. “Tau is associated with death of neurons and development of memory impairment in Alzheimer’s disease,” explains Oskar Hansson, M.D., a neurology professor at Lund University in Sweden and a principal author on the blood test study. Dr. Hansson explains that by identifying a specific variant of tau in the blood, researchers can see the extent to which tau is affecting the brain. “The test is specific for Alzheimer’s and is not elevated in other dementia disorders,” he says.
The JAMA study recruited 1,402 participants, some as young as 25, to test them for Alzheimer’s blood biomarkers. Researchers found that this blood test could detect high levels of plasma P-tau217 up to 20 years before cognitive impairment symptoms may begin to appear. “The test is more specific than MRI and cognitive tests, which are often changed in similar ways in other dementia disorders,” Dr. Hansson says.
New research has paved the way for other Alzheimer’s-specific diagnosis tests, like a spinal fluid test presented in a 2018 study in American Family Physician, which can identify the levels of tau affecting the brain. But, as Dr. Hansson explains, these methods are costly and difficult to access, as opposed to the simplicity and ease with which a blood test could be distributed to clinics around the world.
“This is some of the first research to show that these tests may be even more accurate than we ever imagined they could be,” Edelmayer says. She agrees that there is great potential for this test to be widespread and accessible, similar to routine blood tests that can measure cholesterol, STIs, or thyroid function. “There’s more research that’s needed, but it’s still a very exciting time,” she says.
It’s unclear as of yet what the timeline will be for getting these tests to the public. Dr. Hansson explains that his team plans to continue research on different populations of people to ensure the blood test has a similar level of accuracy for everyone. These trials can often take years, but Edelmayer notes that the Alzheimer’s research field is moving quickly: “I do expect, based on the rapid progress we’ve seen in just the past few years, we’re probably not too far off from seeing these types of tools in the physician’s office.”
Why Early Detection Matters
This all begs the question: Do I want to know if I’m destined to develop Alzheimer’s disease? With no set cure for Alzheimer’s dementia, there’s an arguable case for not wanting to know that you’ll soon start losing your memory. However, research increasingly shows that early detection of Alzheimer’s risk could be key to slowing or stopping the disease progression altogether.
Multiple clinical trials are in progress looking at whether antibodies can be used to reduce or prevent cognitive impairment. Lifestyle changes such as regular exercise, a whole foods diet, a rich social life, and minimizing vascular disease risk can all help slow Alzheimer’s progression. “There are a lot of benefits to early detection and accurate diagnosis,” Edelmayer says. She explains that early detection gives families the power to plan for the future, as well as an incentive to help their loved one change their lifestyle for the better. “There’s also potential to get enrolled and involved in clinical trials where you might see the most benefit at an earliest phase of the disease,” she notes.
Dr. Hansson hopes this blood test will open new avenues to learn about slowing Alzheimer’s progression. “I think this test will facilitate the development of disease modifying therapies that hopefully can slow down or even stop the disease,” he says. Participants could participate in trials that track and monitor their symptoms in the long term, giving experts a better idea of how to stop memory loss from occurring.
“It really is an exciting time for the field right now,” Edelmayer says. “These blood tests are just one example of the efforts that are ongoing to support not only detection and diagnosis, but also will help to support the development of new drugs and therapeutics and interventions in the future.” These small steps all play a role in working toward the seminal goal of an Alzheimer’s cure.