A new study has found a strong link between circadian rhythm and dementia risk.
Published in the medical journal Neurology, researchers found that participants who were more active during a specific window of the day had an increased risk of dementia, a condition characterized by declines in memory, language, reasoning, and problem-solving skills.
Guided by the brain and influenced by light exposure, circadian rhythm is a roughly 24-hour cycle that determines when we become sleepy and when we’re more alert.
In addition to regulating sleep and wake cycles, it also regulates hormones, body temperature and digestion.
For those with a strong circadian rhythm, the body is aligned with the 24-hour day and sticks to a regulated sleep and activity pattern despite seasonal changes or schedule disruptions.
Alternatively, those with a weak rhythm are more likely to see variations in their sleep and activity times.
“Changes in circadian rhythms happen with aging, and evidence suggests that circadian rhythm disturbances may be a risk factor for neurodegenerative diseases like dementia,” said study author Wendy Wang.
“Our study measured these rest-activity rhythms and found that people with weaker and more fragmented rhythms, and people with activity levels that peaked later in the day, had an elevated risk of dementia.”
Researchers reviewed heart monitor data of more than 2,000 participants, 176 of whom were later diagnosed with dementia.
They found that those with low, weaker circadian rhythms had nearly 2.5 times the risk of developing dementia compared to those in the high group.
And those who experienced peak activity later in the afternoon — from 2:15 onward — had a 45% higher risk of dementia compared with earlier in the afternoon between 1:11 and 2:14.
Seven percent of those in the early activity group developed dementia, compared to 10% of those in the later group.
Researchers think that a later peak in activity suggests discord between the body’s clock and environmental cues such as darkness.
“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 Wang.
Wang and her team note that their study did not account for sleep disorders, which could affect the results.
Still, she is hopeful that these findings will inspire further research and preventive measures.
“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 person’s risk of dementia.”
Dementia diagnoses are projected to skyrocket in the coming years, with new cases expected to reach 1 million per year by 2060 if significant intervention isn’t taken.
While the role of circadian rhythm in dementia risk is a burgeoning field of research, the link between sleep and cognitive function is well established.
A study published earlier this year found that night owls may experience cognitive decline faster than early birds.
A 2022 study suggests that seniors who nap more than an hour daily have a 40% higher risk of developing Alzheimer’s disease compared to those who nap less than an hour.
And a 2019 study found that individuals in their 70s who were excessively sleepy during the day were more likely to develop motoric cognitive risk syndrome — a pre-dementia condition.
