UC Berkeley Study Links Sleep Disruption to Alzheimer's Protein Buildup

Episodic memory, which includes recalling personal experiences such as daily activities, tends to weaken with age, particularly in individuals developing Alzheimer’s disease. The researchers observed that as tau proteins accumulate in the brain, particularly in the frontal cortex, the coordinated brain wave patterns during non-REM sleep become erratic.

Sharon noted, "This is the first time we’ve shown this relationship between tau and how it messes with memory consolidation by attenuating traveling slow waves that originate in the frontal cortex."

Non-REM sleep plays a crucial role in brain health, with neurons operating in synchronized slow waves. These waves are essential for effective memory consolidation. In their study, the team compared brain wave measurements through electroencephalograms (EEGs) from cognitively healthy adults in their early 20s with those from older adults aged mid-60s to mid-70s. The younger adults displayed clusters of slow waves that traveled longer distances across the scalp, while older participants exhibited shorter and more solitary wave patterns.

Using positron emission tomography (PET) scans with Dr. William Jagust, the researchers confirmed that tau accumulation in the frontal cortex was linked to the deterioration of these long wave patterns. They found that even in older adults without Alzheimer’s, memory decline correlated with higher tau levels and disrupted sleep waves, suggesting an early indication of cognitive decline.

The research also included measures of memory retention, where participants learned word associations at night and were tested the following day. Those experiencing more solitary, shorter slow waves remembered less information. A long-term follow-up showed that participants with increasing tau levels had worsening slow-wave coordination and memory retention.

Additionally, the team collaborated with neurologist Yo-El Ju to analyze tau levels in the spinal fluid of another elderly group and observed a similar correlation, supporting the initial findings.

Sharon stated, “It’s not just about age; it’s the amount of pathology in frontal areas where global waves originate and the quality of sleep.” Further research will explore the intricacies of these connections and consider potential interventions.

Co-authors of the study include Xi Chen, James Westphal, Chelsea Brown, Vyoma D. Shah from UC Berkeley, and Jason Dude from Washington University in St. Louis. The research was funded by the National Institute on Aging at the NIH, with additional support for Sharon from a Glenn Foundation Postdoctoral Fellowship and a Weill Neurohub Fellowship.