Circadian rhythms which are weaker and extra fragmented are linked to an elevated danger of dementia, in line with a brand new examine printed on December 29, 2025, in Neurology®, the medical journal of the American Academy of Neurology. The examine additionally discovered that circadian rhythm ranges that peaked later within the day, relatively than earlier, have been additionally linked to an elevated danger. The examine doesn’t show that these components trigger dementia, it solely exhibits an affiliation.
Circadian rhythm is the physique’s inner clock. It regulates the 24-hour sleep-wake cycle and different physique processes like hormones, digestion and physique temperature. It’s guided by the mind and influenced by gentle publicity.
With a robust circadian rhythm, the physique clock aligns nicely with the 24-hour day, sending clear alerts for physique capabilities. Folks with a robust circadian rhythm are likely to comply with their common occasions for sleeping and exercise, even with schedule or season modifications. With a weak circadian rhythm, gentle and schedule modifications usually tend to disrupt the physique clock. Folks with weaker rhythms usually tend to shift their sleep and exercise occasions with the seasons or schedule modifications.
Modifications in circadian rhythms occur with growing old, and proof means that circadian rhythm disturbances could also be a danger issue for neurodegenerative illnesses like dementia. Our examine measured these rest-activity rhythms and located folks with weaker and extra fragmented rhythms, and folks with exercise ranges that peaked later within the day, had an elevated danger of dementia.”
Wendy Wang, MPH, PhD, examine creator, Peter O’Donnell Jr. College of Public Well being, UT Southwestern Medical Middle, Dallas, Texas
The examine concerned 2,183 folks with a median age of 79 who didn’t have dementia firstly of the examine. Of individuals, 24% have been Black folks and 76% have been white folks.
Members wore small coronary heart displays that adhere to the chest to measure relaxation and exercise for a median of 12 days. Researchers used knowledge from the displays to trace the power and patterns of individuals’s circadian rhythms. Members have been then adopted for a median of three years and through that point 176 folks have been recognized with dementia.
Researchers reviewed coronary heart monitor knowledge for varied measures to find out circadian rhythm power. These measures included relative amplitude, which is a measure of the distinction between an individual’s most energetic and least energetic intervals. Excessive relative amplitude signified stronger circadian rhythms.
Researchers divided individuals into three teams, evaluating the excessive group to the low group. A complete of 31 of 728 folks within the excessive group developed dementia, in comparison with 106 of the 727 folks within the low group. After adjusting for components resembling age, blood strain and coronary heart illness, researchers discovered when in comparison with folks within the excessive group, these within the low, weaker rhythm group had almost 2.5 occasions the chance of dementia, with a 54% elevated danger of dementia for each commonplace deviation lower in relative amplitude.
Researchers additionally discovered individuals who skilled a peak of exercise later within the afternoon, 2:15 p.m. or later, in comparison with earlier within the afternoon, 1:11 p.m.-2:14 p.m., had a forty five% elevated danger of dementia. Seven % of these within the early group developed dementia, in comparison with 10% of these within the excessive group.
Having a later peak of exercise means there might be a distinction between the physique clock and environmental cues resembling later hours and darkness.
“Disruptions in circadian rhythms might alter physique processes like irritation, and should intervene with sleep, probably rising amyloid plaques linked to dementia, or decreasing amyloid clearance from the mind,” mentioned Wang. “Future research ought to look at the potential function of circadian rhythm interventions, resembling gentle remedy or life-style modifications, to find out if they could assist decrease an individual’s danger of dementia.”
A limitation of the examine was that researchers didn’t have info on sleep issues, like sleep apnea, which may have an effect on the outcomes.
Supply:
American Academy of Neurology
Journal reference:
Wang, W., et al. (2025). Affiliation Between Circadian Relaxation-Exercise Rhythms and Incident Dementia in Older Adults. Neurology. doi: 10.1212/wnl.0000000000214513. https://www.neurology.org/doi/10.1212/WNL.0000000000214513
