The purpose of this study is to measure cerebrospinal fluid (CSF) clearance in subjects with and without high blood pressure. CSF cushions the brain from impact and carries waste products from the brain to the bloodstream. This process is known as clearance. 

Researchers have considered that impaired clearance of amyloid (a protein) from the aging brain causes buildup of amyloid in the brain and plays a role in increased risk for Alzheimer’s disease. It is also suspected that clearance may be related to the health of vessels carrying the blood throughout the brain. It is known that high blood pressure damages blood vessels and thus may impair clearance.  

In this project we will examine if having high blood pressure is related to impaired brain clearance and whether treating high blood pressure improves clearance and reduces buildup of Alzheimer’s disease-related proteins. This study will examine CSF clearance using positron emission tomography (PET) scanning, which creates images of structures in the body and their functioning. This study will also measure the amount of tau in the brain. Tau and amyloid are proteins that build up in the brains of people with Alzheimer’s disease. 

An investigational compound (tracer) called [18F]MK-6240 is injected into the blood prior to the scan in order to take images of the CSF clearance and measure tau protein in the brain. This tracer is considered investigational because it is not approved by the US Food and Drug Administration (FDA) for clinical use and is only being used for research purposes. 

In addition to the assessment of tau amount in the brain with PET study described above, the buildup of Alzheimer’s disease-related proteins will also be examined by directly measuring amyloid and tau in the cerebrospinal fluid. To accomplish this goal we will perform lumbar puncture, also known as a spinal tap.