Sathe, Aditi; Yang, Yisu; Schilling, Kurt G.; Shashikumar, Niranjana; Moore, Elizabeth; Dumitrescu, Logan; Pechman, Kimberly R.; Landman, Bennett A.; Gifford, Katherine A.; Hohman, Timothy J.; Jefferson, Angela L.; Archer, Derek B. “Free-water: A promising structural biomarker for cognitive decline in aging and mild cognitive impairment.” Imaging Neuroscience 2 (2024): 1-15. https://doi.org/10.1162/imag_a_00293.
Diffusion MRI can measure something called “free water” (FW) in the brain, which may help us better predict cognitive problems and memory decline as people age or develop Alzheimer’s disease (AD). FW is very sensitive to small changes in brain tissue, so it might be more useful than traditional brain scans for spotting early signs of trouble.
In this study, researchers looked at how FW measurements in the hippocampus (a part of the brain important for memory) and two brain regions commonly affected by AD relate to thinking and memory skills. They also compared FW results with more traditional brain scan measures, like hippocampal size.
They used data from 296 older adults (average age about 73), some of whom had mild cognitive impairment (MCI), and tracked their brain scans and memory test scores for up to five years. They used a special imaging technique called diffusion MRI and a modeling method to separate out and measure FW in the brain. Then, they ran statistical analyses to see how well different brain measures predicted thinking abilities—both at the beginning and over time.
They found that several brain measurements, including FW levels, were linked to memory performance. Most importantly, FW in the hippocampus was especially good at predicting memory decline over time—better than traditional brain imaging methods. It explained more changes in memory performance than any of the other brain measures studied.
In short, this research suggests that measuring free water in the brain—especially in the hippocampus—might be a powerful tool for detecting and tracking cognitive decline in aging and Alzheimer’s disease.
Fig 1.
Neuroimaging Workflow. The hippocampus and Schwarz/McEvoy AD Signature area segmentations were obtained from the T1 image; the diffusion image was used to calculate conventional and FW-corrected DTI metrics. Next, the structural images were co-registered to the diffusion b0 image. Biomarkers were then estimated. These steps were performed for the baseline imaging visit for each participant.