Alzheimer’s symptoms often diverge from tau levels, study suggests

Cross-sectional differences in atrophy and copathology between Alzheimer’s Disease Neuroimaging Initiative (ADNI) Tau Positron Emission Tomography (Tau-PET) mismatch groups. Credit: JAMA Neurology (2025). DOI: 10.1001/jamaneurol.2025.4974

One of the biggest challenges in treating Alzheimer’s disease (AD) is how heterogeneous it is in terms of speed of decline and presence of other pathologies. That is, more than 50% of people with AD have other pathologies that influence how fast or slow cognitive decline will be.

A study led by Christopher Brown, MD, Ph.D., and David Wolk, MD, from the Perelman School of Medicine at the University of Pennsylvania evaluated people with early Alzheimer’s disease to understand why some individuals show more memory and thinking problems than expected based on the amount of tau protein in their brains—a hallmark of AD—and why others show fewer symptoms than expected. Researchers used brain scans or a blood test to measure tau levels and compared these to clinical assessments of cognitive function.

Participants were grouped into three categories: “vulnerable” people whose symptoms were worse than expected for their tau levels, “canonical” people whose symptoms matched their tau levels, and “resilient” people whose symptoms were milder than expected.

People in the vulnerable group were more likely to have other brain pathologies—such as signs of additional protein abnormalities—and tended to decline cognitively more quickly over time. In contrast, the resilient group declined more slowly, suggesting that factors like brain resilience or “cognitive reserve” help protect against the impact of Alzheimer’s pathology, according to a report published this week in JAMA Neurology.

Importantly, these patterns held true whether tau was measured by a brain scan or a simple blood test, making this approach promising for clinical use. The mismatch between clinical symptoms and tau burden may help doctors better predict disease progression and tailor care for individuals with Alzheimer’s disease.