Circadian rhythm influences dementia diagnosis and disease progression

The time of day blood is drawn can affect the results of tests used to diagnose dementia, according to new research led by the University of Surrey.

Researchers found that the biomarkers used to diagnose Alzheimer’s disease, including a promising marker for early diagnosis of the condition, varied significantly depending on the time of day. Biomarker levels were lowest in the morning when participants woke up and highest in the evening.

The p-tau217 biomarker, which could help in the early diagnosis of dementia, showed large differences depending on the time of day. Researchers found that the variation between morning and evening levels was similar to the changes seen in people whose mild memory problems worsen over a year.

Dr. Ciro della Monica, research fellow at the University of Surrey’s Surrey Sleep Research Center and first author of the publication, said:

This work demonstrates the importance of taking time of day into account when collecting clinical diagnostic samples and how an individual’s clinical picture can be affected by varying sample times. Standardizing the time of day a sample is taken can make diagnosing dementia and monitoring disease progression more accurate.”

Dr. Ciro della Monica, Research Associate, Surrey Sleep Research Centre, University of Surrey

The study looked at 38 participants with mild Alzheimer’s disease, their carers and health checks while they lived at the Surrey Sleep Research Centre, which is part of the UK Dementia Research Institute’s Care Research & Technology Center (UK DRI ).

Instead of taking a single blood sample, as is the case in most clinical practices, participants had blood drawn every three hours for 24 hours.

Four of the five measured biomarkers (p-tau217, Aβ40, Aβ42 and NfL) showed fluctuations during the day. Only GFAP showed no statistically significant variation.

It is currently unknown what causes these time differences. It may be related to sleep and sleep-related reductions in the production or clearance of these markers from the brain into the circulation, meals, posture, activity, or circadian mechanisms. Nevertheless, the findings imply that the time of sample collection is relevant in the implementation and interpretation of plasma biomarkers in dementia research and care. Overall, these findings indicate that the timing of sampling should be standardized or at least recorded.

Professor Derk-Jan Dijk, Director of the Surrey Sleep Research Centre, UK DRI Group Leader and senior author of the publication, said:

“Research on circadian rhythm has shown that almost all variables related to physiology and brain function vary with time of day. This study shows that translating this basic knowledge to the field of dementia research holds great promise for better understanding, diagnosis, and treatment of Alzheimer’s disease. ”