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Exploring the link between intravoxel incoherent motion measured brain diffusivity during wakefulness and sleep
Lena Meinhold1, Misha P T Kaandorp1, Ziyao Shang2
1Center for MR Research, University Children's Hospital, Zurich, Switzerland; University of Zurich, Zurich, Switzerland.
Abstract:
Intravoxel incoherent motion (IVIM) is a diffusion-weighted magnetic resonance imaging (MRI) method that models slow (D, tissue diffusivity) and fast (D*, microvascular perfusion) signal components (f, signal fraction). This observational study explores the relationship between IVIM metrics and sleep macrostructure and physical activity levels in nineteen healthy elderly individuals (mean age 72.2 ± 5.0). Participants underwent two MRI sessions during wakefulness, four weeks apart, on a GE 3T Premier scanner. IVIM parameters (D, D*, f and their product fD*) were calculated using non-linear least-squares and a deep learning transformer-based estimator and analysed across seven regions of interest. Sleep was recorded at home on 10-14 consecutive nights, following each MRI scan, using a portable electroencephalography (EEG) system. Physical activity was recorded in parallel with actigraphy. Associations were tested using linear mixed effects models, with activity included in sensitivity analyses. Better EEG-derived sleep quality and higher physical activity were predominantly linked to lower estimated values for IVIM fD*. These findings may reflect differences in microvascular perfusion and/or the cerebrospinal fluid compartment associated with sleep and warrant further investigation of the mechanisms linking IVIM metrics to sleep quality. Clinicaltrials.gov: NCT05539378, trial registry name: Exploring the Link Between Sleep and Brain Clearance (BBCDS).
Insights
Better sleep quality and increased physical activity in healthy older adults were associated with lower Intravoxel Incoherent Motion (IVIM) fD* values. These findings suggest a link between microvascular function, sleep, and activity levels.
Area of Science:
- Neuroimaging
- Gerontology
- Sleep Science
Background:
- Intravoxel Incoherent Motion (IVIM) is a diffusion-weighted MRI technique measuring tissue diffusivity (D) and microvascular perfusion (D*, f).
- Understanding the relationship between brain microcirculation, sleep, and physical activity in aging is crucial for cognitive health.
Purpose of the Study:
- To investigate the association between IVIM parameters and sleep macrostructure in healthy elderly individuals.
- To explore the correlation between IVIM metrics and physical activity levels in the same cohort.
Main Methods:
- Observational study involving 19 healthy elderly participants (mean age 72.2±5.0).
- Two MRI sessions using a GE 3T Premier scanner to acquire IVIM data.
- Sleep macrostructure assessed via portable EEG (10-14 nights); physical activity monitored with actigraphy.
- IVIM parameters (D, D*, f, fD*) calculated using non-linear least-squares and a deep learning transformer-based estimator.
Main Results:
- Higher physical activity and better EEG-derived sleep quality were predominantly associated with lower estimated IVIM fD* values.
- These associations were observed across seven regions of interest.
- Sensitivity analyses including physical activity supported the primary findings.
Conclusions:
- Lower IVIM fD* values in healthy older adults may be linked to improved sleep quality and higher physical activity.
- Findings suggest potential alterations in microvascular perfusion or cerebrospinal fluid dynamics related to sleep and activity.
- Further research is warranted to elucidate the mechanisms connecting IVIM metrics, sleep quality, and brain health.
