A new study published in the Journal of Affective Disorders examined whether an advanced measure from an MRI test, called free-water imaging , can help in the early identification of brain processes related to Alzheimer's — even in people who appear cognitively normal.

The study focuses on a particularly important question: Is it possible to identify silent brain changes, even before a person begins to experience memory decline or before family members notice functional difficulty? As the field advances, it is becoming clear that early diagnosis of Alzheimer's and cognitive decline does not rely solely on memory tests, but also on biomarkers, brain imaging, and long-term follow-up.

What did they investigate?

The researchers used data from 276 adults who participated in the Harvard Aging Brain Study. All participants were cognitively normal at the start of the study.

They underwent advanced diffusion MRI tests, from which a measure called cortical free-water was calculated. This measure may reflect subtle changes in brain tissue, such as inflammatory processes, microscopic damage, or early changes in the brain's cellular environment.

Participants also underwent PET scans for amyloid and tau, as well as cognitive monitoring over time. The researchers examined whether higher levels of free-water were associated with tau accumulation, amyloid, future cognitive decline, or progression to mild cognitive decline.

What did they find?

The researchers found that higher levels of cortical free-water were associated with tau accumulation in certain brain regions, particularly the entorhinal cortex and the pons. These regions are relevant to memory, recognition, and information processing, and are thought to be particularly important in the early stages of Alzheimer's disease.

However, the index was not as closely related to overall amyloid burden. That is, it appears that free-water may reflect more processes related to nerve injury and tau, and not necessarily the presence of amyloid itself.

Additionally, higher levels of free-water predicted faster cognitive decline and a higher risk of progression to MCI—mild cognitive decline. This association remained significant even after the researchers took into account amyloid status and cortical thickness.

What are the conclusions?

The study suggests that free-water imaging may be a sensitive measure of early brain changes, even in people who are still functioning well and not diagnosed with cognitive decline.

The importance of the finding is that it may add information beyond more familiar measures, such as amyloid, tau, or brain atrophy. In the future, advanced MRI measures may help identify who is at higher risk for cognitive decline, even before the decline is noticeable in daily life.

However, it is important to emphasize: this is an observational study, not a routine clinical examination. It does not mean that every adult should undergo an advanced MRI, and it does not allow for a certain prediction of what will happen to a particular person. This is a promising research tool, which requires further validation before widespread use in the community or in memory clinics.

What are the recommendations for the public?

The message to the public is that early diagnosis of cognitive decline is very advanced, but there is still no substitute for a thorough medical evaluation.

If a person or their family members notice a change in memory, orientation, language, decision-making, or daily functioning, it is important to contact a family doctor or a memory clinic. In many cases, a check-up is necessary that includes blood tests, a review of medications, a cognitive assessment, mood and sleep testing, and sometimes brain imaging.

The study reminds us that the brain may undergo changes years before obvious signs appear. That's why early detection is important, as is maintaining overall health: exercise, controlling blood pressure, managing diabetes and cholesterol, getting enough sleep, maintaining social connections, and eating a healthy diet — all part of a broader picture of maintaining brain health.

The main message from the study:

Advanced free-water MRI may help identify early brain changes associated with tau and risk of cognitive decline, even in people who appear cognitively normal. This is a promising research direction for earlier diagnosis, but is not yet a routine screening test for the public.

The full article:

• Link:
  https://doi.org/10.1016/j.jad.2025.121108

• Reference:

He, H., Zhang, C., Yu, D., Gao, X., Wei, C., & Ding, W. (2026). Free-water imaging predicts cognitive decline and clinical progression in cognitively normal older adults. Journal of Affective Disorders, 398, 121108. https://doi.org/10.1016/j.jad.2025.121108

The content is intended to make scientific information accessible to the public and does not constitute medical advice.