New research explores how daily rhythms relate to brain health
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A study of more than 2,000 older adults found that weaker or irregular circadian rhythms were linked to a higher risk of developing dementia.
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Participants wore monitors for about 12 days so researchers could track patterns of rest and activity throughout the day.
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People whose activity peaked later in the afternoon had a 45% higher risk of dementia compared with those who peaked earlier.
Most people think of the bodys internal clock known as the circadian rhythm as the thing that helps regulate sleep. But it actually does much more. This internal timing system coordinates the bodys 24-hour cycle, helping regulate sleep and wake patterns, hormones, digestion and body temperature.
Now, new research published in Neurology, the medical journal of the American Academy of Neurology, suggests that these daily rhythms may also be linked to dementia risk.
Researchers found that people with weaker or more irregular circadian rhythms were more likely to develop dementia over time. They also observed a connection between the timing of a persons daily activity and dementia risk. Importantly, the study only shows an association it does not prove that changes in circadian rhythm directly cause dementia.
Still, scientists say the findings highlight how the bodys natural rhythms may play a role in brain health as people age.
Changes in circadian rhythms happen with aging, and evidence suggests that circadian rhythm disturbances may be a risk factor for neurodegenerative diseases like dementia, researcher Wendy Wang, MPH, Ph.D., said in a news release.
Our study measured these rest-activity rhythms and found people with weaker and more fragmented rhythms, and people with activity levels that peaked later in the day, had an elevated risk of dementia.
The study
The study involved 2,183 older adults with an average age of 79 who did not have dementia when the research began. Participants were part of the long-running Atherosclerosis Risk in Communities (ARIC) study conducted at several U.S. research centers.
To measure circadian rhythms, participants wore small heart-monitor patches that also captured movement data for an average of 12 days. The devices allowed researchers to track patterns of rest and activity throughout each 24-hour cycle.
Using this data, scientists calculated several indicators of circadian rhythm health. These included the strength of a persons daily rhythm, how fragmented their activity patterns were during the day, and the timing of when their activity levels peaked.
Participants were then followed for about three years. During that time, researchers monitored medical records and assessments to identify who developed dementia.
What the study found
By the end of the follow-up period, 176 participants about 8% of the group had been diagnosed with dementia.
Researchers found that people with weaker circadian rhythms had a significantly higher risk of dementia compared with those whose rhythms were stronger and more consistent. In fact, those in the lowest rhythm-strength group had nearly 2.5 times the risk.
The timing of daily activity also appeared to matter. People whose activity levels peaked later in the afternoon at about 2:15 p.m. or later had a 45% higher risk of developing dementia compared with those whose activity peaked earlier.
The researchers note that circadian rhythms naturally change with age, and disruptions to these rhythms may be tied to neurodegenerative diseases. However, more research is needed to understand whether improving circadian rhythms through approaches such as light exposure or lifestyle changes could help reduce dementia risk.
For now, the findings offer another piece of the puzzle in understanding how daily biological rhythms may influence long-term brain health.
Disruptions in circadian rhythms may alter body processes like inflammation, and may interfere with sleep, possibly increasing amyloid plaques linked to dementia, or reducing amyloid clearance from the brain, said Dr. Wang. Future studies should examine the potential role of circadian rhythm interventions, such as light therapy or lifestyle changes, to determine if they may help lower a persons risk of dementia.
Posted: 2026-03-05 19:40:35



















