Study Links Weaker Circadian Rhythms to Higher Dementia Risk in Older Adults

While the research does not establish a direct cause-and-effect relationship, it reveals an important connection between daily activity patterns and brain health, according to findings published in Neurology®, the medical journal of the American Academy of Neurology.

The study, led by Dr. Wendy Wang at the Peter O’Donnell Jr. School of Public Health at UT Southwestern Medical Center, focused on the potential link between disrupted circadian rhythms and dementia. Dr. Wang noted that changes in circadian rhythms are common with aging, and disturbances in these rhythms may serve as a risk factor for neurodegenerative conditions like dementia.

The research involved 2,183 older adults, averaging 79 years of age, who were dementia-free at the study's start. Participants wore heart monitors for about 12 days to record their rest and activity patterns. After three years of follow-up, 176 participants were diagnosed with dementia.

To evaluate circadian rhythm strength, researchers measured relative amplitude, indicating the difference between active and inactive periods of the day. Participants were categorized into three groups based on their rhythm strength. In the high-strength group, 31 out of 728 developed dementia, whereas 106 out of 727 in the low-strength group were diagnosed. After adjusting for factors like age and heart health, the results showed that individuals in the weaker rhythm group had approximately 2.5 times the risk of developing dementia. Additionally, for every standard decrease in relative amplitude, the dementia risk rose by 54 percent.

The timing of daily activity peaks also played a role. Participants who peaked later, after 2:15 p.m., exhibited a higher dementia risk compared to those whose activity peaked earlier, between 1:11 p.m. and 2:14 p.m. Specifically, 10% of those with later peaks developed dementia, compared to 7% in the earlier peak group, reflecting a 45% increased risk.

Dr. Wang suggested that disruptions in circadian rhythms could impact bodily processes like inflammation and sleep, potentially increasing the presence of amyloid plaques associated with dementia or hindering their clearance from the brain.

Future research may focus on whether interventions such as light therapy or changes in lifestyle could mitigate dementia risk by strengthening circadian rhythms. The study did not address sleep disorders like sleep apnea, which may also influence circadian rhythms and brain health.

Despite this limitation, the findings offer valuable insights into how daily habits and circadian rhythms relate to the risk of dementia.