A study published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association has revealed that older adults with disrupted circadian rhythms may experience brain atrophy in regions typically affected by Alzheimer’s disease. Researchers found that those with a more fragmented daily rest-activity rhythm showed more significant shrinking in areas related to memory and emotion.
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The study involved participants wearing wrist accelerometers for up to a week to track their 24-hour activity patterns, alongside MRI scans of the parahippocampal gyrus, hippocampus, and amygdala—regions commonly impacted by Alzheimer’s.
Adam Spira, PhD, a senior author and professor at Johns Hopkins University, noted that while disturbed sleep has been linked to poor brain health, the relationship between rest-activity rhythms and changes in brain structure was less understood. The data indicated how often participants shifted between activity and rest.
According to Marc Kaizi-Lutu, a doctoral researcher at Johns Hopkins, fragmented rhythms reflect frequent transitions between activity and rest, whereas less fragmented rhythms involve longer, more sustained periods of each.
The findings indicated that participants with more consistent rest-activity patterns had larger brain volumes in memory-related areas and less shrinkage of the amygdala, which is crucial for emotional processing. Daniel Callow, PhD, also a co-author of the study, highlighted that these results suggest that irregular rhythms could precede structural changes in the brain, potentially contributing to neurodegeneration.
Additionally, researchers observed a link between fragmented rhythms and a quicker increase in the volume of brain ventricles—fluid-filled spaces that often expand as brain tissue deteriorates.
Dung Trinh, MD, who was not involved in the study, emphasized the significance of the findings, pointing out that a more fragmented rest-activity rhythm correlates with faster brain atrophy and smaller brain volumes in key areas associated with memory and emotion. He noted the importance of maintaining brain volume for overall well-being as individuals age.
Trinh offered suggestions for improving circadian rhythm regularity to potentially enhance brain health, including waking up at the same time daily, getting morning light exposure, staying active, maintaining mealtime consistency, avoiding late naps, and limiting substances like caffeine and alcohol before bedtime. However, he cautioned that the study demonstrates an association, not causation, and recommended discussing sleep-related issues with healthcare providers.