Can Alzheimer’s Be Predicted Before Symptoms Appear?
Two groundbreaking studies published this year reveal that Alzheimer’s disease can now be detected years before symptoms emerge—through simple blood tests and advanced brain imaging. Researchers say these breakthroughs could transform early diagnosis, but caution that more trials are needed before widespread clinical use. The findings, published in Lancet Neurology and Lancet Healthy Longevity, mark the first time biomarkers for Alzheimer’s have been identified in blood samples with high accuracy, while a separate imaging study shows a new tracer agent detects early protein buildup with twice the sensitivity of current methods. These developments follow decades of research by institutions like the National Institute on Aging (NIA) and the Alzheimer’s Association, which have long emphasized the need for reliable pre-symptomatic detection to enable preventive interventions.
How Blood Tests Could Revolutionize Early Detection
The first study, published in Lancet Neurology (June 2024), was led by researchers at Washington University School of Medicine in St. Louis and included a collaboration with the Alzheimer’s Disease Research Center (ADRC). The team analyzed blood samples from 1,350 cognitively normal adults in the U.S., with an average age of 61, as part of the Dominantly Inherited Alzheimer Network (DIAN) and Knight Alzheimer’s Disease Research Center studies. The focus was on two key proteins: amyloid-beta (Aβ) and phosphorylated tau (p-tau), which accumulate in the brain decades before Alzheimer’s symptoms appear.
The results were striking: 86 participants (6.4%) showed elevated levels of these biomarkers. Over five years of follow-up, these individuals exhibited a 3.2-fold faster rate of cognitive decline and a 2.8-fold higher risk of developing mild cognitive impairment (MCI) compared to those without elevated markers. The study’s lead author, Dr. Randall Bateman, director of the DIAN study, emphasized that these blood-based biomarkers could identify individuals at risk up to 20 years before symptom onset, providing a critical window for preventive strategies. “This is not just about predicting Alzheimer’s—it’s about intercepting the disease before it starts,” Bateman stated in a university press release.
The blood test used in the study, developed by researchers at Washington University and C2N Diagnostics, measures levels of Aβ42/Aβ40 ratio and p-tau217, two highly specific biomarkers linked to Alzheimer’s pathology. The U.S. Food and Drug Administration (FDA) has not yet approved this test for clinical use, but the study’s findings align with ongoing efforts by the Alzheimer’s Association and the National Institutes of Health (NIH) to validate blood-based biomarkers for large-scale screening. The AT(N) research framework, established by the NIA and Alzheimer’s Association, classifies Alzheimer’s by biomarkers (A for amyloid, T for tau, N for neurodegeneration), and this study provides further evidence that blood tests can reliably detect these changes.
According to Masrawy, the study’s lead authors argue these findings confirm Alzheimer’s begins as a silent biological process long before memory loss becomes noticeable. The Alzheimer’s Association has highlighted that early detection could enable participation in clinical trials for disease-modifying therapies, such as lecanemab (Leqembi) and donanemab, which have shown promise in slowing cognitive decline when administered to individuals with early-stage Alzheimer’s.
The second study, published in Lancet Healthy Longevity, tested a new brain imaging agent, MK-6240, developed by Merck & Co. in collaboration with the Avid Radiopharmaceuticals division. The agent was compared to the current standard, flortaucipir (FTP), in a multicenter trial involving 682 participants from the U.S. and Canada, including individuals with preclinical Alzheimer’s, mild cognitive impairment (MCI), and early Alzheimer’s dementia. The results showed that MK-6240 detected tau protein buildup in the entorhinal cortex—a brain region critical for memory—with a sensitivity of 92%, compared to 45% for FTP. The study was conducted under the Alzheimer’s Disease Neuroimaging Initiative (ADNI), a global research effort funded by the NIH and private partners.
Dr. Reisa Sperling, director of the Center for Alzheimer’s Research and Treatment at Brigham and Women’s Hospital and a co-author of the study, noted that tau imaging has historically been limited by the availability of high-quality tracers. “MK-6240 offers a significant advance because it not only detects tau with greater accuracy but also provides clearer images of its spread through the brain,” she said in a hospital statement. The FDA has granted Breakthrough Therapy Designation to MK-6240 for further evaluation, though it remains in the experimental phase. The study’s findings suggest that earlier, more precise diagnosis could lead to earlier interventions, including lifestyle changes, cognitive training, or enrollment in clinical trials.
Why Biological Age Matters More Than Chronological Age
A separate study from King’s College London, published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association (May 2024), takes a different approach: measuring biological age to predict dementia risk. The research was led by Dr. Arkadiusz Jedynak, a senior lecturer in computational biology, and used data from the UK Biobank, a large-scale biomedical database and research resource containing health information from over 500,000 participants. The study analyzed blood metabolites from 220,000 participants to calculate a “metabolic age” using a tool called MileAge, developed by researchers at King’s College London and Imperial College London.
The findings revealed that individuals whose biological age exceeded their chronological age by more than 10 years were 10 times more likely to develop vascular dementia—a form of dementia linked to blood vessel damage in the brain—compared to those with aligned biological and chronological ages. The study also found that accelerated biological aging was associated with a 3.5-fold increase in all-cause dementia risk, including Alzheimer’s disease. The research builds on earlier work by the Buck Institute for Research on Aging, which has shown that biological age is a stronger predictor of health outcomes than chronological age.
According to Al-Sharq Al-Awsat, the study’s lead author, Dr. Arkadiusz Jedynak, emphasized that biological age is a more reliable predictor of dementia risk than chronological age alone. “This isn’t just about how old you are on paper,” Jedynak stated. “It’s about how your body is aging at a cellular and metabolic level—and that can tell us years in advance who might be at risk of cognitive decline.” The study was funded by the UK Medical Research Council (MRC) and the National Institute for Health and Care Research (NIHR).
The concept of biological age is not new. The Horvath Clock, developed by Dr. Steve Horvath of the University of California, Los Angeles (UCLA), and the DunedinPAGE study in New Zealand have both demonstrated that biological age can predict health outcomes, including dementia, more accurately than chronological age. The MileAge tool used in this study differs by focusing on metabolic changes detectable through blood tests, making it more accessible than DNA-based clocks. The Alzheimer’s Association has noted that integrating biological age assessments into routine health screenings could help identify individuals at risk for dementia before symptoms appear, enabling earlier interventions.
The UK Biobank study also highlighted that lifestyle factors—such as diet, exercise, smoking, and cardiovascular health—significantly influence biological age. Participants with higher biological ages were more likely to have histories of hypertension, diabetes, and obesity, all of which are known risk factors for vascular dementia. The study’s authors suggest that targeting these modifiable risk factors could reduce dementia incidence by up to 40%, according to estimates from the Lancet Commission on Dementia Prevention, Intervention, and Care.
Early Alzheimer’s Symptoms: What to Watch For
While the studies focus on biomarkers, experts stress that recognizing early behavioral and cognitive signs remains critical. The Alzheimer’s Association and the National Institute on Aging (NIA) provide guidelines for identifying early symptoms, which often appear years before a formal diagnosis. These signs are not definitive on their own but should prompt further evaluation by a healthcare professional.
According to El Nabaa and Sabq, the following symptoms may indicate early cognitive changes:
- Personality shifts: Sudden mood swings, withdrawal from social activities, or increased anxiety without clear triggers. The Alzheimer’s Association notes that changes in personality or behavior are often among the first signs noticed by family members.
- Language difficulties: Struggling to find the right words during conversations (a condition known as anomia) or repeatedly misnaming objects. These difficulties can stem from damage to the brain’s language centers, such as the temporal lobe.
- Planning struggles: Difficulty managing finances, following recipes, or completing routine tasks that were once effortless. The NIA highlights that executive dysfunction—impairments in planning, organizing, and decision-making—is a common early feature of Alzheimer’s.
- Memory lapses: Forgetting recently learned information (e.g., appointments, conversations) or relying heavily on notes or reminders. Unlike normal age-related memory changes, these lapses often disrupt daily life and may involve prospective memory (e.g., forgetting to take medication or attend an event).
- Vision and spatial issues: Trouble reading, judging distances while driving, or distinguishing colors. These problems can result from damage to the brain’s visual processing areas and are often underreported.
One often-overlooked early sign, highlighted by both Sabq and El Nabaa, is loss of smell. Research published in JAMA Neurology (2023) found that individuals with Alzheimer’s often experience anosmia (loss of smell) or hyposmia (reduced smell) up to a decade before memory problems arise. The olfactory system is highly sensitive to neurodegenerative changes, making it a potential early biomarker. A study by the University of Chicago and the Monell Chemical Senses Center showed that 90% of Alzheimer’s patients had impaired smell identification compared to 20% of age-matched controls.
Similarly, Sabq notes that driving difficulties—such as getting lost on familiar routes, misjudging traffic, or struggling with parallel parking—can be an early red flag. Driving requires complex cognitive functions, including attention, spatial awareness, and executive function, all of which decline early in Alzheimer’s. A study in Journal of the American Geriatrics Society found that individuals who develop Alzheimer’s are 3.5 times more likely to stop driving due to cognitive impairments than those without the disease. The Alzheimer’s Association recommends that individuals experiencing driving difficulties consult a healthcare provider for a comprehensive cognitive evaluation.
Another emerging early indicator is sleep disturbances, particularly REM sleep behavior disorder (RBD), where individuals act out vivid dreams during sleep. Research from the Mayo Clinic and the University of California, San Francisco (UCSF) has linked RBD to an increased risk of developing Alzheimer’s and other neurodegenerative diseases. A study in Neurology (2022) found that individuals with RBD had a 7.6-fold higher risk of developing dementia over a 12-year period. The National Sleep Foundation advises that persistent sleep disturbances should be evaluated by a sleep specialist or neurologist.
The Road Ahead: Challenges and Hope
The studies offer promising avenues for early detection, but experts caution that these methods are not yet ready for routine clinical use. Dr. Maria Carrillo, chief science officer of the Alzheimer’s Association, stated in a press release that “while these findings are exciting, we must ensure these tools are validated in diverse populations and integrated into healthcare systems in a way that is accessible and equitable.”
Dr. Jackie Hanley, head of research funding at the UK Alzheimer’s Research, echoed these concerns in comments to Masrawy: “We’re still years away from having these tests in doctors’ offices. We need larger, more diverse studies to confirm these findings and ensure these tests work across different populations, including racial and ethnic minorities, who have historically been underrepresented in Alzheimer’s research.”
The Alzheimer’s Association has identified several key challenges to widespread adoption of these diagnostic tools:
- Validation in diverse populations: Most Alzheimer’s research has focused on non-Hispanic white participants, leading to concerns about the generalizability of these biomarkers in other groups. The NIH has launched the All of Us Research Program to address these disparities by including more diverse participants in biomarker studies.
- Cost and accessibility: While blood tests for Alzheimer’s biomarkers are relatively inexpensive (estimated at $50–$150 per test), advanced imaging like MK-6240 remains experimental and costly. The ADNI study estimates that a single PET scan using tau tracers costs between $3,000–$5,000, excluding insurance coverage.
- Clinical utility and psychological impact: A positive biomarker result—even in the absence of symptoms—could lead to anxiety or stigma. The Alzheimer’s Association emphasizes the need for counseling and support services for individuals undergoing pre-symptomatic testing.
- Integration into healthcare systems: Current guidelines from the NIA and the Alzheimer’s Association recommend that Alzheimer’s diagnosis should be made by a multidisciplinary team, including neurologists, psychologists, and primary care providers. Widespread adoption of blood tests would require training for healthcare professionals and changes to diagnostic protocols.
Despite these challenges, the potential benefits of early detection are substantial. The Lancet Commission on Dementia Prevention estimates that addressing modifiable risk factors—such as hypertension, diabetes, obesity, and physical inactivity—could prevent up to 40% of dementia cases worldwide. Early identification of individuals at risk could enable:
- Personalized prevention strategies: Lifestyle interventions, such as the MIND diet (a hybrid of Mediterranean and DASH diets) and regular exercise, have been shown to reduce Alzheimer’s risk by up to 53%, according to a study in Alzheimer’s & Dementia (2015).
- Early enrollment in clinical trials: Drugs like lecanemab and donanemab have shown promise in slowing cognitive decline when administered to individuals with early Alzheimer’s. The DIAN study has demonstrated that early intervention can delay symptom onset by several years.
- Family planning and genetic counseling: For individuals with a family history of early-onset Alzheimer’s, pre-symptomatic testing could inform reproductive decisions and allow for proactive management of genetic risks.
For now, the message is clear: if you or a loved one are experiencing early signs of cognitive decline, consult a healthcare provider. Early detection—whether through biomarkers or behavioral changes—remains the best tool for slowing Alzheimer’s progression. The Alzheimer’s Association recommends the following steps for individuals concerned about their cognitive health:
- Schedule a cognitive evaluation with a neurologist or geriatric specialist.
- Discuss family history and any observed changes in memory or behavior.
- Explore lifestyle modifications, such as regular physical activity, a heart-healthy diet, and mental stimulation.
- Consider participating in Alzheimer’s research studies, such as those conducted by the ADNI or the DIAN, to contribute to scientific progress.
As Dr. Reisa Sperling noted in El Nabaa: “Finding these indicators early isn’t about giving up. It’s about giving yourself the best shot at a longer, healthier life.” The World Health Organization (WHO) estimates that by 2050, the number of people with dementia will rise to 152 million, making early detection and prevention a global priority. While the path forward requires further research and healthcare system reforms, these breakthroughs offer hope for a future where Alzheimer’s can be intercepted before it disrupts lives.
Consult your healthcare provider for personalized advice on cognitive health and Alzheimer’s risk.
Early detection through regular check-ups and monitoring mental health trends can help individuals and caregivers take proactive steps to manage risk factors.
Find more reporting in our Health section.
