The role of cardiovascular insults on aging changes in brain structure and vascular function and their cognitive outcomes.
The goal of this study is to use non-invasive methods for quantitative measurements of brain vascular function and structure in community dwelling subjects drawn from the Dallas Heart Study - uT Southwestern alzheimer Disease Center (Study id: STu 052011-037). These measurements will be associated with measures of aortic stiffness and cognitive testing obtained as part of the parent study.
For this study, the participants will be asked to lay down in the magnet with minimal movement. The scan session will first start with a few anatomical imaging protocols to localize the brain and to allow identification of our regions of interest. Then the blood supply to the brain will be measured using an MRi technique. How the brain blood supply changes with physiological stimulation will also be measured. The subject will perform a carbogen breathing task. a mouthpiece is put into the subject's mouth. The other end of the mouth piece is connect to a two-way valve, either connecting to the room air or connecting to a plastic bag filled with 5% Co2, 21% o2 and 74% n2. The valve will be switched by the researcher to control the kind of air the subject is breathing. The extra Co2 that the bag air contains is known to cause vasodilation and an increase in cerebral blood flow. The purpose of this task is to test the cerebrovascular reserve of the subject. The hypothesis is that some participants will have reduced cerebrovascular reserve and that this inability to increase blood flow as needed (as in the case of extra Co2 in the breathing air) will result in impaired cognitive function.
in this task that is known to cause hypercapnia (the Co2 amount in the lung and in the blood is higher than normal conditions. This can test whether or not the blood vessels in the brain can dilate when needed) and vasodilation (blood vessels increase their diameters to attract more blood flow to the brain), the subject will breathe using their mouth instead of the nose. The mouth is holding a plastic tube. The other end of the tube is either connected to room-air or to a large bag containing 5% Co2, 21% o2 and 74% n2. The only difference between this gas mixture and the air is that Co2 level is higher (from 0.033% to 5%). This, again, is expected to increase blood flow. We will switch the valve back and forth every minute so that the subject is breathing room air for one minute, then 5% Co2 for one minute, then back to room air and so on. The subject will do this task for a total of 10 minutes. a staff will be inside the magnet room throughout the task to monitor their performance and behavior. it is important to emphasize that such a hypercapnia task (5% Co2) has been used by many previous studies in other institutions. in our own laboratory, we have also tested the task on more than 40 subjects and all subjects tolerated the task well. Heart rate, blood pressure and arterial oxygenation will be continuously monitored during the task.
The study will consist of one visit. Prior to this MRi examination participants will have participated in detailed cognitive testing from a separate ongoing study run by the uT alzheimer Disease Center (Study id: STu 052011-037). The informed consent procedure, safety screen, and preparation for the chosen task will take approximately 30 minutes and the MRi scan will take approximately 60 minutes, giving a total of 90 minutes for the visit. all experiments will be performed on a 3.0 Tesla MR system. in this project, we will study a total of 80 participants.
each MRi session will use the following MRi sequences: localizer, 3D T1-weighted sequence, T2-weighted FLaiR sequence, MR angiogram, MR venogram, aSL sequence for CBF measurement, venous oxygenation measurement sequence, and cerebral blood volume sequence. The total scan duration for each subject will be approximately 60 minutes. no contrast agent injection or any other invasive procedure will be used.
Dallas Heart Study participants with imaging obtained at the first and second phases who agree to participate in further evaluation in an ongoing study with the UT Southwestern Alzheimer Disease Center (IRB 052011-037) are eligible. Specifically candidates will be:
* Ages 55+
* All races and ethnicities
* Able to read, speak, and understand English (The cohort of subjects that this study will recruit from, i.e. the subjects participating in a longitudinal study in conjunction with the Dallas Heart Study and the Alzheimer[Single Quote]s Center, are all English-speaking subjects.)