Can a blood test predict dementia? 4 latest studies show promise

• Medical Information At the moment has collated its current protection round blood exams for detecting dementia early, which might support prognosis years earlier than signs seem.
• One examine suggests {that a} blood check might assist predict the chance of dementia in older ladies as much as 25 years earlier than the onset of signs.
• One other examine finds {that a} blood check that screens modifications within the intestine microbiome might assist diagnose dementia earlier.
• The opposite two research measure blood ranges of phosphorylated tau 217 (pTau217), a biomarker of dementia, in addition to tau and beta-amyloid.

Round 74% of Americans with Alzheimer’s disease, a kind of dementia, are ages 75 years or older, in line with the Alzheimer’s Affiliation. The situation also can develop in folks underneath 65 years of age. This is named younger-onset or early onset dementia.

Having the ability to detect indicators of dementia as early as potential and display screen for the potential threat might assist to enhance remedy outcomes or decelerate the development of the illness.

Medical Information At the moment seems at its protection of 4 current research on detecting Alzheimer’s illness early through means aside from mind scans — one blood check primarily based on modifications within the intestine microbiome, and one other three primarily based on the proteins tau and beta-amyloid and their variants.

A examine revealed in The Lancet in Could 2026 examined the feasibility of blood-based biomarker exams to detect early indicators of cognitive decline in adults between the ages of 53 and 69 and not using a dementia prognosis.

Among the many contributors, round 6% had excessive blood ranges of proteins tau and beta-amyloid. 5 years later, the identical people skilled better cognitive decline in contrast with those that didn’t have excessive ranges of beta-amyloid and tau.

In a previous interview with Medical Information At the moment, Megan Glenn, PsyD, medical neuropsychologist within the Middle for Reminiscence and Wholesome Growing older on the Hackensack Meridian Neuroscience Institute at Jersey Shore College Medical Middle in New Jersey, who was not concerned on this examine, mentioned:

“Now we have recognized for a very long time that refined cognitive modifications and organic markers, notably amyloid accumulation, start creating a long time earlier than a affected person meets the standards for a proper dementia prognosis.”

“Now we have been trying to find accessible methods to detect these earliest indicators throughout this ‘preclinical’ section so we will intervene sooner, and this examine represents a serious step towards making early detection scalable and accessible to most of the people,” she mentioned.

A cohort examine of two,766 older ladies, revealed in JAMA Network Open in March 2026, discovered that the protein plasma phosphorylated tau 217 (pTau217) might assist predict indicators of dementia as much as 25 years earlier than signs seem.

At the beginning of the examine, contributors had no reminiscence or cognitive issues. Starting from 1 to 25 years later, those that had increased ranges of pTau217 — of which there have been 1,311 contributors — had skilled delicate cognitive decline or dementia.

The examine famous some affiliation between increased pTau217 ranges, dementia, and elements equivalent to age and genetics. For instance, these carrying the APOE ε4 gene and people older than 70 years skilled a extra vital cognitive decline.

Whereas such biomarkers might assist predict dementia years earlier than signs seem, additional analysis is important.

Ebrahim Zandi, Ph.D., affiliate professor of immunology and immune therapeutics on the College of Southern California, who was not concerned within the examine, commented on the examine’s limitations in a previous interview with MNT.

“The cohort consisted completely of older postmenopausal ladies, limiting applicability to males or youthful populations,” he mentioned.

“Though the examine examined racial subgroups and impact modification, pattern sizes in minority teams have been smaller, and APOE knowledge weren’t uniformly accessible throughout all teams. This raises necessary questions on biomarker thresholds and efficiency throughout various populations,” he added.

In a examine revealed in Nature Communications in April 2026, researchers discovered that the pTau217 biomarker might assist detect indicators of cognitive decline sooner than exams equivalent to PET scans can. Brain scans are historically used to assist diagnose dementia.

For a median of 8 years, the examine adopted 317 adults ages between 50 and 90 years who didn’t have any considering or reminiscence issues initially of the examine.

These with increased ranges of pTau217 initially of the examine skilled quicker cognitive decline. The examine famous that increased pTau217 ranges have been linked with a better accumulation of the amyloid-beta protein, the buildup of which experts believe could also be the primary reason behind Alzheimer’s illness.

“There are already 2 FDA-approved pTau217 blood exams in medical use. As extra knowledge accumulate, blood exams — particularly pTau217 — seem like pretty much as good as, and even higher than, cerebrospinal fluid testing and present glorious concordance with amyloid-β PET.”

Researchers from the College of East Anglia in the UK studied the connection between Alzheimer’s illness and microbe-derived metabolites (MDMs), waste merchandise produced by intestine micro organism, publishing their leads to Gut Microbes.

The examine concerned analyzing blood and stool samples of 15 adults ages 50 years and older. Some contributors had no indicators of cognitive impairment, whereas others had delicate cognitive impairment or subjective (self-reported) cognitive impairment.

The researchers used machine studying to look at the 33 metabolites they recognized within the samples. They discovered decrease ranges of key neuroprotective metabolites, which help mind well being, in folks with delicate or subjective cognitive impairment.

The identical people additionally had elevated ranges of a cytotoxic metabolite, indoxyl sulfate, suggesting that decrease ranges of neuroprotective metabolites or increased ranges of cytotoxic metabolites might point out cognitive decline.

In a previous interview with MNT, Dung Trinh, MD, an internist with MemorialCare Medical Group and the chief medical officer of the Wholesome Mind Clinic in Irvine, CA, who was not concerned within the examine, spoke about these findings.

“[The study] suggests {that a} small panel of blood metabolites linked to food regimen and the intestine microbiome might assist determine folks with very early cognitive modifications, which is thrilling as a result of we’d like much less invasive methods to detect threat sooner,” he mentioned.

“On the similar time, this was a comparatively small, cross-sectional examine, so it reveals affiliation fairly than proving that these markers can reliably predict who will go on to develop dementia,” he added.