Reviewed by the Help Dementia Editorial Team — our editors review every article for accuracy against guidance from the National Institute on Aging, the Alzheimer’s Association, and peer-reviewed sources.
Proteins involved sits at the center of this dementia and brain health question.
The proteins implicated in Alzheimer’s disease—the same proteins that form plaques and tangles in diseased brains—may paradoxically help preserve normal memory and cognitive function in healthy aging. Recent research suggests these proteins serve dual roles: when properly regulated and maintained, they can protect the brain from cognitive decline, even in people whose brains contain hallmark Alzheimer’s pathology. This apparent contradiction reveals a fundamental truth about brain aging: the presence of disease-related proteins does not automatically mean cognitive decline, and the factors that keep these proteins beneficial in normal brains may offer insights into preventing Alzheimer’s dementia. A landmark 2024 Nature study examined 48 post-mortem brains—26 from people who had experienced Alzheimer’s symptoms and 22 from cognitively normal individuals—and discovered something remarkable.
Some of the cognitively normal subjects had brains filled with amyloid plaques, the hallmark of Alzheimer’s disease, yet they had maintained sharp thinking and memory throughout their lives. The difference lay in a specific protein called Reelin, which acts like a structural support system for brain cells. Those who aged without cognitive decline had higher levels of Reelin and more neurons capable of producing it. This finding upends the assumption that amyloid accumulation alone determines cognitive fate, pointing instead to protective mechanisms that operate even when Alzheimer’s pathology is present.
Table of Contents
- What Makes Some Proteins Protect the Brain While Others Damage It?
- The Reelin Discovery—How Researchers Identified Neuroprotection in Alzheimer’s Brains
- Beyond Reelin—The Complex World of Multiple Protective Proteins
- Using Protein Signatures to Predict Cognitive Decline—Practical Implications
- Important Limitations and Cautions When Interpreting Protein Research
- Connecting Laboratory Discoveries to Everyday Brain Health
- The Path Forward—From Protein Research to Dementia Prevention
- Conclusion
What Makes Some Proteins Protect the Brain While Others Damage It?
The brain is far more complex than a simple accumulation of toxic proteins. The same proteins involved in Alzheimer’s disease pathology perform essential functions during normal brain aging and cognitive maintenance. Reelin is a prime example: it originally helped build the brain’s architecture during early life, organizing how neurons connect and communicate. But its role doesn’t end in childhood. Throughout life, Reelin continues to support neural connections and maintain cognitive resilience, acting as a natural buffer against the very pathology—amyloid and tau tangles—that would otherwise lead to memory loss and dementia. What determines whether a protein becomes protective or destructive is often context and quantity.
Reelin levels, neural stability, inflammatory responses, and how these factors interact all influence whether a person with Alzheimer’s pathology maintains normal cognition or experiences decline. The September 2023 analysis of 427 individuals found that those who maintained sharper cognitive function as they aged had more neurons producing Reelin throughout their brains. In other words, the brain’s capacity to produce protective proteins—not the absence of disease proteins—emerged as a key predictor of healthy aging. This distinction matters because it shifts focus from simply clearing away “bad” proteins to enhancing the brain’s natural protective mechanisms. A person whose brain effectively maintains Reelin and other protective proteins may tolerate amyloid accumulation without experiencing memory problems, while another person with less Reelin but fewer plaques might develop cognitive decline. The brain’s own defense systems, not the disease burden alone, determine cognitive outcomes.
The Reelin Discovery—How Researchers Identified Neuroprotection in Alzheimer’s Brains
The 2024 Nature study provided some of the most compelling evidence yet that cognitive resilience in aging isn’t simply about avoiding Alzheimer’s pathology—it’s about having the right protective proteins in place. Researchers compared the brains of cognitively normal older adults with those who had developed Alzheimer’s symptoms, looking specifically at cellular and molecular differences. The finding that Reelin-producing neurons were significantly higher in cognitively preserved brains, even when amyloid plaques were present, suggested Reelin functions as a neuroprotective factor independent of plaque burden. This discovery resolved a long-standing puzzle in Alzheimer’s research: why do some older adults with extensive amyloid and tau pathology remain cognitively intact while others decline? The answer, at least in part, involves protective proteins like Reelin. When Reelin is abundant in the brain, it appears to compensate for pathological changes, maintaining neural communication and memory formation even under challenging circumstances.
Think of it like a structural engineer: the presence of cracks in a building (amyloid plaques) is less important than the quality of the remaining support beams (Reelin). A well-engineered building with good beams can tolerate some damage without collapsing. One important limitation of this research is that it examined post-mortem brains, capturing a snapshot at the end of life rather than showing how Reelin changes throughout the aging process or whether increasing Reelin could actually prevent or delay cognitive decline. The study also involved a relatively small sample size (48 brains), though the findings align with larger longitudinal studies like the September 2023 analysis that tracked hundreds of living participants over time. Researchers caution against assuming that simply boosting Reelin will prevent Alzheimer’s in everyone, as the interplay between protective and harmful proteins is intricate and varies among individuals.
Beyond Reelin—The Complex World of Multiple Protective Proteins
While Reelin has captured research attention, it is far from the only protein involved in maintaining cognitive health during aging. A 2025 Southeast Asian cohort study identified a 12-protein plasma signature that significantly predicted cognitive decline, suggesting that the brain’s protection relies on a coordinated ensemble of proteins rather than a single savior molecule. These 12 proteins work together, and their combined signal proved far more predictive of future cognitive problems than any single protein alone. Even more striking, 10 of the 12 proteins independently predicted incident dementia, meaning that disturbances in any of these proteins could signal increased risk. This research identified specific proteins of concern—including ACES and IGFALS—as particularly associated with baseline Alzheimer’s diagnosis in that cohort.
A separate 2025 longitudinal study identified six additional proteins linked to incident Alzheimer’s dementia: ACES, C7, ZCD1, IL-17C, CC055, and SO5A1. Some proteins appear on multiple studies’ danger lists, while others emerge specifically in certain populations or disease stages, reflecting how Alzheimer’s pathology involves 16 distinct biological processes affecting everything from immune function to protein transport to neuroinflammation. The complexity here offers both hope and caution. It means that cognitive decline likely involves multiple pathways, and understanding these pathways opens multiple avenues for intervention—researchers can target any of several processes to potentially slow or prevent decline. But it also means there is no single protein test or simple preventive treatment likely to work for everyone. A person’s cognitive destiny involves the interactions among dozens of proteins and biological systems, shaped by genetics, lifestyle, environment, and chance.
Using Protein Signatures to Predict Cognitive Decline—Practical Implications
The real power of modern protein research lies in prediction. If scientists can identify which protein patterns signal upcoming cognitive decline, people at risk might have an opportunity to intervene before memory problems emerge. A 2025 multi-cohort analysis involving 2,139 participants across four different studies examined plasma proteomes—the complete set of proteins circulating in the blood—and linked them to various hallmarks of Alzheimer’s pathology and cognitive function. This represents one of the largest coordinated efforts to understand how blood proteins reflect brain changes. What emerged was encouraging on one front and sobering on another. When researchers combined plasma protein data with standard clinical risk factors—like age, apolipoprotein E genetic status, and cognitive test scores—their predictive accuracy for cognitive outcomes jumped dramatically from an area under the curve (AUC) of 0.62 to 0.85.
In practical terms, this means that a doctor using this combined protein-plus-clinical approach could distinguish between people likely to experience cognitive decline and those likely to remain stable with substantially greater accuracy than using traditional methods alone. This could help identify candidates for early intervention, monitoring, or lifestyle changes before dementia develops. However, a significant gap remains between identifying risk and preventing it. Knowing that someone has a risky protein pattern is only valuable if interventions exist to change that pattern. Currently, most protein-based findings are recent discoveries without established treatments targeting those specific proteins. Additionally, the studies establishing these protein signatures come from diverse populations and healthcare systems; what works to predict decline in a Southeast Asian cohort may not apply equally to other ethnic groups or geographic regions. Implementing protein screening in routine clinical practice also raises questions about cost, access, and how to communicate risk to patients without causing unnecessary anxiety.
Important Limitations and Cautions When Interpreting Protein Research
While protein research offers promise, critical limitations deserve emphasis. Most current protein studies are observational, meaning researchers measure proteins and then observe whether people develop cognitive decline—but this does not prove that the proteins caused the decline or that changing them will prevent it. Correlation and causation are not the same. A protein signature might be a marker of an ongoing biological process rather than the driving force behind that process, much like how smoke indicates fire but spraying water on smoke alone won’t extinguish the flames. Another limitation is that plasma proteins—those floating in the blood—are not the same as proteins in the brain itself. The blood-brain barrier prevents most large molecules from crossing freely, so what we measure in a blood test may not perfectly reflect what’s happening in the brain.
Some of the 16 biological processes implicated in cognitive decline, such as neuroinflammation or amyloid clearance, involve brain-specific processes that blood proteins only approximate. Furthermore, nearly all the 2025 protein studies identifying specific risk proteins (ACES, C7, ZCD1, and others) are extremely recent, meaning they lack long-term follow-up data and independent replication in different populations. What seems strongly predictive today might appear less important as more data accumulates. Genetics also complicates the picture. Some people may naturally produce protective proteins in abundance due to their genes, while others face an uphill battle regardless of lifestyle. A person with a genetic predisposition for low Reelin production might not benefit as much from interventions targeting Reelin as someone whose genes support higher production. This means that personalized medicine approaches based on individual protein profiles will likely be necessary for effective prevention, rather than one-size-fits-all recommendations.
Connecting Laboratory Discoveries to Everyday Brain Health
Understanding that protective proteins like Reelin and others support normal memory has practical implications for how people approach brain health during aging. While the research is primarily laboratory-based so far, it suggests that activities and choices known to support brain health—such as aerobic exercise, cognitive engagement, quality sleep, social connection, and Mediterranean-style diets—might work partly by maintaining levels of protective proteins. These lifestyle factors are known to reduce Alzheimer’s risk, and protein research provides a possible explanation: they help the brain maintain its natural defenses. For someone concerned about cognitive aging, the message is not to wait for a protein test or future medication based on Reelin research.
The protective factors identified in research—education, physical activity, cognitive stimulation, stress management, cardiovascular health, and social engagement—remain the most evidence-based approaches currently available. These factors have the advantage of being accessible, having multiple health benefits beyond brain protection, and carrying minimal risk. Whether they work through maintaining Reelin, supporting other protective proteins, or through entirely different mechanisms, their benefits for cognitive aging are well-established. The protein research helps explain why these interventions matter, even if it doesn’t yet point to shortcuts.
The Path Forward—From Protein Research to Dementia Prevention
The convergence of Reelin research, multi-protein signatures, and large-scale proteomics studies suggests that the next decade of Alzheimer’s prevention may involve identifying and supporting protective protein systems long before dementia develops. Blood-based biomarkers, including protein signatures, are likely to play an increasing role in identifying people at risk, allowing intervention when the brain might still be most responsive to prevention efforts. This shift from treating advanced disease to preventing early decline represents a fundamental change in how medicine might approach Alzheimer’s. However, discovering proteins associated with protection is different from developing interventions based on that knowledge.
Researchers are working toward therapies that could boost Reelin, modulate the other 12 proteins in the protective signature, or address the 16 biological processes involved in cognitive decline. Some of these therapies might come from drugs, while others could emerge from advances in understanding how lifestyle factors influence protein production and function. The timeline for such developments is uncertain, potentially years or decades away for each specific target. For now, protein research has fundamentally shifted the narrative around Alzheimer’s: the disease is not simply about accumulation of harmful proteins, but about the balance between protective and harmful factors, the brain’s capacity for resilience, and the multiple biological systems that influence whether aging leads to cognitive preservation or decline. This more nuanced understanding opens new research directions and offers hope that Alzheimer’s may one day be preventable through targeted interventions—whether those interventions work through supporting Reelin, managing other protective proteins, or supporting the biological pathways that keep brains healthy.
Conclusion
The discovery that proteins implicated in Alzheimer’s disease may simultaneously support normal memory and cognitive function during healthy aging represents a major shift in understanding brain health. Proteins like Reelin, along with the 12-protein signature and the 16 biological processes identified in recent studies, do not fit into simple categories of “good” or “bad”—instead, they operate within complex systems where their abundance, regulation, and interaction with other proteins determine whether aging brains remain cognitively robust or decline toward dementia. Some people maintain normal memory despite having their brains filled with Alzheimer’s pathology, specifically because they have higher levels of protective proteins like Reelin.
Moving forward, the practical steps remain largely unchanged from current recommendations: maintain cardiovascular health, stay cognitively and socially engaged, exercise regularly, prioritize sleep, manage stress, and pursue activities that bring meaning and connection. Simultaneously, emerging blood-based protein tests and biomarker research may soon allow earlier identification of people at risk, potentially opening windows for prevention before cognitive decline begins. As researchers work to understand how to boost protective proteins and intervene in the multiple biological pathways contributing to dementia, the insight that our brains harbor natural defense systems offers both encouragement and direction.
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For more, see Alzheimer’s Association — clinical trials.
