Fragmented Circadian Rhythms Linked to Higher Dementia Risk: Study
USA: Prospective data published in Neurology show that older adults with weaker and more fragmented circadian rhythms have an increased risk of developing dementia. These findings highlight the potential role of disrupted sleep–wake cycles as an early marker or modifiable risk factor for dementia.
In a new analysis from the Atherosclerosis Risk in Communities (ARIC) Study, Wendy Wang from the Department of Internal Medicine at UT Southwestern Medical Center, Dallas, Texas, and colleagues examined how objectively measured rest–activity rhythms relate to future dementia risk in a racially diverse population of older adults. Circadian rhythms, which regulate daily patterns of activity and rest, are known to change with aging, but their contribution to neurocognitive decline remains incompletely understood.
The researchers retrospectively analyzed 2,183 ARIC participants without dementia who wore a Zio XT ECG patch for at least three days in 2016–2017. The device also recorded accelerometer data to measure rest–activity rhythms, assessing rhythm strength, fragmentation, consistency, and peak activity timing using nonparametric and cosinor metrics.
Participants had a mean age of 79 years, 58% were women, and nearly 25% were Black. Patches were worn for an average of 12 days. Dementia outcomes were tracked through 2020 via cognitive assessments, hospital records, and death certificates. Over a median three-year follow-up, 176 participants (8%) developed dementia.
Key findings were as follows:
- Several circadian rhythm characteristics were independently associated with the risk of developing dementia after adjustment for demographic and clinical factors.
- Lower relative amplitude, indicating weaker overall circadian rhythm strength, was strongly linked to future dementia.
- Each one standard deviation decrease in relative amplitude was associated with a 54% higher risk of dementia.
- Greater intradaily variability, reflecting more fragmented daily rest–activity patterns, was associated with an increased dementia risk.
- Lower amplitude measures were independently linked to elevated dementia risk in adjusted analyses.
- Lower mesor, another indicator of reduced rhythm robustness, was also associated with a higher likelihood of developing dementia.
- A later acrophase, representing delayed peak daily activity, was associated with a substantially higher risk of dementia.
- Both the strength and timing of circadian rhythms appeared to be important determinants of brain health in older adults.
The authors note that their findings were consistent across Black and White participants, strengthening the generalizability of the results. However, they also acknowledge important limitations, including the absence of dementia subtype information and the lack of objective measurements for specific sleep disorders such as sleep apnea.
Overall, the study adds to growing evidence that circadian rhythm disruption may play a role in the development of dementia. The use of accelerometer data from a widely used ambulatory cardiac monitor highlights a practical approach to assessing circadian health in large populations.
The researchers emphasize that future studies are needed to determine whether interventions aimed at strengthening or stabilizing circadian rhythms could help reduce dementia risk in older adults.
Reference: https://www.neurology.org/doi/full/10.1212/WNL.0000000000214513
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