"My memory is getting worse — am I getting dementia?"
It is the most common opening line in a neurology clinic, and the heaviest one. The answer is often unexpected: there are many causes of memory loss, and Alzheimer's disease is only one of them.
This article covers three things worth understanding before anyone books a scan: why memory loss deserves a proper work-up, what a single blood test can actually show, and how to read the result without reading too much into it.
1. When memory slips, do not diagnose yourself first
All of the following cause forgetfulness and poor concentration, and most of them are reversible:
- Lifestyle — chronic sleep deprivation, late nights, exhaustion.
- Mood — anxiety and depression, among the commonest causes of "forgetfulness" in middle age.
- Underlying disease — hypertension, high cholesterol, diabetes, thyroid dysfunction, vitamin deficiency.
- Medication — long-term use of some sleeping tablets and sedatives also drags on memory.
The first step after noticing a decline is therefore a baseline work-up: routine blood tests and brain MRI, clearing the reversible causes out of the way first.
2. Sometimes the work-up should go further
If the routine tests are all normal and memory keeps sliding, a dedicated Alzheimer's assessment becomes worthwhile. There are two reasons.
First, according to the NIA-AA research framework published in Alzheimer's & Dementia in 2018, the pathological phase of Alzheimer's disease lasts more than a decade. By the time symptoms are obvious, the damage is often already at a stage that is hard to reverse.
Second, diagnosis based on symptoms alone is unreliable. Research from the University of Washington School of Medicine indicates that roughly one in three clinical diagnoses of Alzheimer's made on cognitive symptoms alone prove to be wrong.
Confirmation has traditionally required brain PET imaging or lumbar puncture for cerebrospinal fluid — accurate, but expensive, invasive and of limited availability. That is why the field has turned to a far simpler entry point: blood.
3. Why a blood sample can see what is happening in the brain
The core pathology of Alzheimer's disease is the abnormal accumulation of amyloid-beta (Aβ) and tau protein in the brain. These processes are not sealed inside the skull: changes in the brain leak into the peripheral bloodstream in minute quantities.
A new generation of ultra-sensitive assays captures exactly that — changes in phosphorylated tau, particularly p-tau217 — and uses them to reflect the pathological state of the brain indirectly.
How credible is the technique? A 2024 validation study published in Nature Medicine by teams from the University of Washington School of Medicine and Lund University in Sweden — drawing on 1,422 participants in the Swedish BioFINDER-2 cohort and 337 in the University of Washington Knight ADRC cohort — found that p-tau217 blood testing identified amyloid pathology with 95–97% accuracy, comparable to FDA-approved cerebrospinal fluid testing and, in assessing tau pathology, better than it.
In 2025 the clinical practice guidance issued at the Alzheimer's Association International Conference (AAIC) recommended blood biomarker testing as part of the diagnostic pathway for the first time. In May 2025, the first Alzheimer's blood test based on the p-tau217/Aβ42 ratio received FDA clearance. Blood screening had moved from research into clinical practice.
4. Five questions one blood draw can answer
5. Who should be tested — and how to read the result
Priority groups: people over 45 with a family history of Alzheimer's, the "three highs" (hypertension, high cholesterol, diabetes) or long-standing sleep problems; everyone over 60; and anyone whose memory is steadily declining, at any age.
It also has to be said plainly: a blood test is an excellent screening and triage tool, but it is not a verdict. A 2026 real-world validation study from the Mayo Clinic published in JAMA Neurology found that FDA-cleared blood tests carry a meaningful false-positive risk in routine clinical settings. A negative result is largely reassuring; a positive result needs to be read alongside cognitive scales and, where necessary, confirmed by PET or cerebrospinal fluid testing.
The correct approach is for a specialist to integrate history, cognitive scales, imaging and laboratory results into one judgement — not for a single laboratory report to pronounce sentence on its own. That is what evidence-based medicine asks of us.
Alzheimer's disease smoulders for more than a decade. "We'll deal with it when there are symptoms" is the most expensive kind of waiting. Early screening is not about manufacturing anxiety; it is about giving a family something solid to stand on. When memory keeps declining, seek an assessment and let a clinician decide what comes next.
About Dr. Feng Wang
Dr. Feng Wang is a neurologist and associate chief physician at SinoUnited Health. She graduated from Shanghai Jiao Tong University School of Medicine with a master's degree and a doctorate in neurology, has more than 20 years of clinical experience in Shanghai tertiary A hospitals, and spent a year as a visiting scholar at the Brain Research Centre of the Royal Melbourne Hospital in Australia.
Her work has long centred on stroke green-channel development at Shanghai tertiary A hospitals — acute cerebrovascular rescue and standardised, full-course management of cerebrovascular disease — and she has extensive experience in cerebral infarction, cerebral small vessel disease and secondary prevention of stroke recurrence. She focuses on the overlap between cerebrovascular disease and cognitive impairment: screening high-risk vascular patients, systematic assessment and individualised intervention for memory decline, slowed thinking and post-stroke cognitive decline, and differentiating vascular cognitive impairment from Alzheimer's disease and other dementias. She also manages vascular risk factors such as diabetes, hypertension and hyperlipidaemia as an integrated whole, and provides long-term care for cerebral small vessel disease, recurrent dizziness and chronic neurological conditions in older adults. She works alongside sleep specialists to offer middle-aged and older patients a continuous pathway across cerebrovascular, cognitive and sleep health.
She is a council member of the Second Youth Council of the Chinese Stroke Association; secretary of the Cerebrovascular Disease Group, Neurology Branch, Shanghai Medical Association (10th committee); secretary of the Neurology Branch of the Shanghai Stroke Association; a member of the 10th Youth Committee of the Neurology Branch of the Shanghai Medical Association; and a member of the Youth Committee of the Fourth Shanghai Medical Association Stroke Branch.
References
- Barthélemy NR, et al. Highly accurate blood test for Alzheimer's disease comparable or superior to clinical CSF tests. Nature Medicine. 2024.
- Jack CR Jr, et al. NIA-AA Research Framework. Alzheimer's & Dementia. 2018.
- Alzheimer's Association International Conference (AAIC) 2025 clinical practice guidance on blood biomarkers. Alzheimer's & Dementia. 2025.
- US FDA clearance of the Lumipulse pTau217/Aβ42 plasma test, May 2025.
- Algeciras-Schimnich A, et al. Variability in clinical performance of the FDA-cleared Lumipulse p-Tau217/β-Amyloid 1-42 plasma ratio. JAMA Neurology. 2026.
- Liao W, et al. Effectiveness, safety and biomarker dynamics of lecanemab in a Chinese Alzheimer's disease population (SAIL study). Alzheimer's & Dementia. 2026.
This article is health education for international patients and their families and does not replace an individual consultation, examination or diagnosis. Cognitive symptoms have many causes; assessment and any testing decision should be made by a qualified clinician.