Tau linked to isolated sleep waves and memory loss in older adults

Researchers at the University of California, Berkeley studied young adults in their early twenties alongside older participants in their mid-60s to mid-70s. Using EEG recordings, which measure electrical activity in the brain during sleep, they measured how far slow waves travelled across the scalp during deep sleep. In younger participants, waves moved together across distances roughly equivalent to a hand's width. In older adults, they travelled shorter distances and appeared more independently.

Tau and isolated sleep waves

Using brain scans that map the distribution of specific proteins, the researchers found that greater build-up of tau in the frontal part of the brain was linked to less coordinated slow waves. Tau is a protein that forms tangles inside nerve cells in Alzheimer's disease. Crucially, this link was present in people who had not developed Alzheimer's.

Participants learned word pairs in the evening and were tested the following morning. Those whose slow waves travelled shorter distances and appeared more isolated recalled fewer word pairs on average. The researchers also examined cerebrospinal fluid from a separate group of older adults. People with more isolated sleep waves had higher ratios of tau to amyloid, another protein associated with Alzheimer’s, in their spinal fluid.

A window into early memory changes

A subset of participants was followed over several years. As frontal cortex tau levels increased, slow waves became less coordinated and overnight memory retention declined. The study identifies an association between early Alzheimer’s-related protein changes and disrupted sleep-dependent memory, but does not establish a direct causal link.

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Search terms to explore further: slow wave sleep memory consolidation | tau build-up frontal cortex | deep sleep cognitive decline aging