Evaluating Glymphatic Activity Using Noninvasive MRI Techniques in the Bunkyo Health Cohort

In recent years, the glymphatic system hypothesis has gained attention as a brain clearance system. The glymphatic system is a glial-based perivascular network that facilitates the removal of metabolic waste from the brain. In animal models, lifestyle-related diseases such as hypertension, diabetes, and hyperlipidemia, which are risk factors for arterial sclerosis, along with a history of head trauma, have been reported to affect the activity of glymphatic system drainage pathways. However, little is known about how these factors affect the glymphatic system in humans. Therefore, we non-invasively evaluated glymphatic system activity using MRI in cohorts from the Bunkyo Health Study, focusing on elderly individuals with type 2 diabetes, metabolic syndrome, and experience in contact sports. Perivascular space (PVS) volume fraction, fractional volume of extracellular-free water (FW), and an index of diffusion tensor imaging along the perivascular space (DTI-ALPS) were used as indirect indicators of glymphatic activity. As a result, abnormalities in these MRI indicators were observed in elderly individuals with type 2 diabetes, metabolic syndrome, and experience in contact sports. Additionally, these indicators showed significant correlations with cognitive function. This presentation provides an overview of the findings from these studies.