Time of Day Impacts Dementia Diagnostic Test Results, Study Finds

New research reveals that the timing of blood tests can significantly affect biomarker levels used to diagnose Alzheimer’s disease.

Summary: A University of Surrey study shows that dementia biomarker levels in blood samples vary throughout the day, potentially affecting diagnosis accuracy and disease monitoring.

Estimated reading time: 5 minutes

Researchers at the University of Surrey have uncovered a crucial factor that could impact the diagnosis and monitoring of Alzheimer’s disease: the time of day when blood samples are taken. Their study, published in Translational Psychiatry, demonstrates that key biomarkers used in dementia diagnosis fluctuate significantly over a 24-hour period.

The findings have important implications for how dementia tests are conducted and interpreted, potentially affecting millions of patients worldwide.

Biomarker Fluctuations: A Game-Changer for Diagnosis

The study, conducted at the Surrey Sleep Research Centre, part of the UK Dementia Research Institute’s Care Research & Technology Centre, examined 38 participants. The group included individuals with mild Alzheimer’s disease, their caregivers, and healthy older adults.

Unlike standard clinical practices that rely on a single blood sample, researchers collected blood from participants every three hours for a full 24-hour period. This comprehensive approach revealed striking variations in biomarker levels throughout the day.

Dr. Ciro della Monica, research fellow at the Surrey Sleep Research Centre and first author of the study, emphasized the significance of these findings:

“This work shows the importance of considering the time of day when taking clinical diagnostic samples and how the clinical picture for an individual may be affected by varying sample times. By standardising the time of day that a sample is taken, the diagnosis of dementia and tracking disease progression can become more accurate.”

Key Findings: P-tau217 and Other Biomarkers

The study focused on several biomarkers associated with Alzheimer’s disease and other forms of dementia:

P-tau217 (phosphorylated tau)
Amyloid-beta 40 (Aβ40)
Amyloid-beta 42 (Aβ42)
Neurofilament light (NfL)
Glial fibrillary acidic protein (GFAP)

Four out of the five biomarkers (p-tau217, Aβ40, Aβ42, and NfL) showed significant fluctuations throughout the day. Only GFAP did not display statistically significant variation.

Of particular interest is the p-tau217 biomarker, which has shown promise for early diagnosis of Alzheimer’s disease. Researchers found that the variation between morning and evening levels of p-tau217 was comparable to the changes observed in individuals with mild cognitive impairment over the course of a year.

Implications for Dementia Research and Care

The study’s findings have far-reaching implications for both research and clinical practice in the field of dementia:

Diagnostic accuracy: Standardizing the time of day for blood sample collection could improve the accuracy of dementia diagnoses.
Disease progression monitoring: Consistent sampling times may lead to more reliable tracking of disease progression.
Clinical trials: Accounting for time-of-day variations could enhance the evaluation of potential treatments in clinical trials.
Personalized medicine: Understanding individual biomarker fluctuations could lead to more tailored treatment approaches.

Professor Derk-Jan Dijk, Director of the Surrey Sleep Research Centre and senior author of the study, highlighted the broader implications of this research:

“Circadian rhythm research has demonstrated 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 area of dementia research holds great promise for a better understanding, diagnosis and treatment of Alzheimer’s.”

Unanswered Questions and Future Research

While the study provides valuable insights, several questions remain unanswered:

What drives these time-of-day differences in biomarker levels?
How do factors such as sleep, meals, posture, and activity influence biomarker fluctuations?
Are there individual differences in biomarker rhythms that could impact diagnosis or treatment?

Future research will likely explore these questions, potentially leading to more refined diagnostic protocols and treatment strategies for Alzheimer’s disease and other forms of dementia.

As the global population ages and the prevalence of dementia increases, studies like this one underscore the importance of continually refining our approaches to diagnosis and treatment. By considering the impact of time-of-day on biomarker levels, clinicians and researchers may be able to provide more accurate diagnoses, better track disease progression, and ultimately improve outcomes for millions of people affected by dementia worldwide.

Quiz: Test Your Knowledge

Which biomarker showed the most significant time-of-day variation in the study? a) GFAP b) NfL c) P-tau217 d) Aβ40
How often were blood samples taken from participants in the study? a) Once a day b) Every 6 hours c) Every 3 hours d) Every hour
What was the total duration of the blood sampling period in the study? a) 12 hours b) 24 hours c) 36 hours d) 48 hours

Answers:

c) P-tau217
c) Every 3 hours
b) 24 hours

Glossary of Terms

Biomarker: A measurable indicator of a biological state or condition, often used for disease diagnosis or monitoring.
P-tau217: A form of phosphorylated tau protein, considered a promising biomarker for early Alzheimer’s disease diagnosis.
Amyloid-beta (Aβ): Protein fragments that can accumulate in the brain, forming plaques associated with Alzheimer’s disease.
Neurofilament light (NfL): A protein released when neurons are damaged, used as a marker of neurodegeneration.
Glial fibrillary acidic protein (GFAP): A protein found in certain brain cells, elevated levels may indicate brain injury or disease.
Circadian rhythm: The body’s internal 24-hour cycle regulating various physiological processes.

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