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Hourly Variations in Glymphatic Function Based on MRI Scan Times in Cognitively Normal Individuals
Ji Su Ko1, Yangsean Choi2, Eunseon Jeong2
1Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Centre, Seoul, Republic of Korea (J.S.K., Y.C., E.J., J.E.P., H.S.K.); Department of Radiology, Kangbuk Samsung Hospital, Seoul, Republic of Korea (J.S.K.).
Glymphatic function, measured by diffusion tensor image analysis along the perivascular space (DTI-ALPS), is lowest during the daytime. Circadian timing is crucial for accurate glymphatic function assessment.
Area of Science:
- Neuroscience
- Radiology
- Physiology
Background:
- The glymphatic system clears waste from the brain.
- Its function may vary with time of day, impacting brain health.
- Diffusion tensor image analysis along the perivascular space (DTI-ALPS) is a key method for assessing glymphatic function.
Purpose of the Study:
- To evaluate diurnal variations in glymphatic function using DTI-ALPS.
- To determine if MRI scan timing influences glymphatic function assessment.
Main Methods:
- Retrospective cohort study of 539 cognitively normal participants.
- Participants grouped by MRI scan time: dawn, early morning, daytime, evening/night.
- Glymphatic function assessed using the ALPS index derived from DTI; statistical analyses included ANOVA and regression.
Main Results:
- The highest mean ALPS index (glymphatic function) was observed in the dawn group.
- Daytime scans showed significantly lower ALPS index values compared to dawn and early morning.
- Regression analysis confirmed lower daytime glymphatic function, most pronounced compared to the dawn group.
Conclusions:
- Glymphatic function exhibits diurnal variation, with reduced activity during daytime.
- Circadian timing is a critical factor for interpreting DTI-ALPS results.
- Further research is warranted to understand individual glymphatic fluctuations.
