Alzheimer's blood tests aren't ready for the worried well, doctors say

New blood tests capable of flagging Alzheimer's-related proteins years before symptoms appear may appeal to people anxious about later-life dementia, but specialists say the tests are not yet ready for that use — and that lowering risk does not require one.

The U.S. Food and Drug Administration has cleared four blood tests to help doctors determine whether Alzheimer's, rather than another form of dementia or a different condition, is causing a patient's memory or cognitive problems. Some laboratories and online services market their own versions. A faster diagnosis can help people in the early stages of Alzheimer's access drugs that modestly slow symptom progression.

Yet dementia specialists report that people without symptoms are also seeking these tests, even though they are neither approved nor recommended for that group. Testing expert Nicholas Ashton of Arizona's Banner Health said the "worried well" should not be getting them outside a research study.

Instead, doctors point to modifiable brain risks. One large study found that people who reached middle age without high blood pressure, diabetes and smoking remained dementia-free for nearly 13 years longer than those who had all three conditions in their 50s. Dr. Josef Coresh of NYU Langone Health, the study's senior author, advised an aggressive approach, noting that even delaying these conditions "has a huge payoff."

Mark Yost, 60, of Phoenix, understands the impulse. Having watched a loved one succumb to Alzheimer's, he wants to know his own status and what he could do to avoid or slow the disease. He volunteered for a Banner blood test study that included cognitively normal people and learned his result was "intermediate" — possibly some amyloid, but not a worrisome elevated level. He called the uncertainty "a little disappointing" and something to monitor as he ages, while pursuing brain-healthy habits such as exercise and a mentally stimulating genealogy hobby.

Alzheimer's has no known cause, but its hallmark markers are abnormal forms of two proteins. Sticky beta-amyloid can accumulate into brain-clogging plaque over decades, eventually triggering neuron-killing tau tangles that produce symptoms. Blood tests measuring a tau type called p-tau217 appear particularly good at reflecting amyloid buildup in people who already have symptoms.

For those without symptoms, a study led by Mass General Brigham researchers found that older adults with very high p-tau217 levels faced a 38% risk of developing cognitive impairment within five years, and a higher risk over a decade. Ashton cautioned that a positive result is only a risk factor, not a guarantee of future Alzheimer's. Many older adults carry high amyloid levels without ever showing cognitive trouble, and while negative results seem fairly reliable, a positive test can sometimes be a false positive.

A major trial last year found that healthier habits slowed age-related cognitive decline in older adults at increased dementia risk. The steps included a half-hour of moderately intense exercise four times a week, twice-weekly resistance training and the MIND diet, which emphasizes leafy greens, berries, whole grains, poultry and fish. Experts also recommend adequate sleep, avoiding social isolation, treating hearing loss and exercising the brain as well as the body, with middle age a key time to act.

The NYU study reinforces that what benefits the heart benefits the brain. Coresh's team analyzed health records of more than 12,000 people tracked for decades since they were, on average, 56. High blood pressure, Type 2 diabetes and smoking can damage blood vessels that feed the brain and fuel inflammation. Those who entered the study without all three problems fared best, but avoiding one or two still helped. Even carriers of the APOE4 gene, which raises the risk of later-life Alzheimer's, benefited from a healthier middle age. Other research has shown that aggressively treating high blood pressure supports brain health.

Coresh urged patients to be "very serious" with their physicians about lowering blood pressure as early as possible for as many years as possible. As for the blood tests, clinical trials are underway to determine whether drugs now used to treat Alzheimer's might also help certain people before symptoms develop — findings that could change testing advice.