Brain Blood Flow: Age and Gender

Study Overview
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Brief Summary
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Baseline cerebral blood flow through the middle cerebral artery (MCA) and cerebral vasodilator response of the MCA to inhaled carbon dioxide (CO2) will be measured in young women, young men, older women, and older men using Magnetic Resonance (MR) imaging and transcranial Doppler ultrasound (TCD). Data collection techniques will be compared.

Detailed Description
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The investigators have recently shown that cerebral blood flow responses to chemical stimuli are reduced in healthy older adults. The investigators also have preliminary data suggesting that sex differences in cerebrovascular regulation exist. The overall goal of this application is to extend on the investigators previous studies by employing advanced neuroimaging techniques to enhance the investigators understanding of neurovascular coupling in healthy aging. This study will collect clinically significant data with implications for the future risk of cognitive decline and Alzheimer's disease. The research aims are: To determine the effect of age and sex on baseline cerebral blood flow through the middle cerebral artery (MCA). To determine the effect of age and sex on cerebral vasodilator responses. To determine if the cerebrovascular responses measured by transcranial Doppler ultrasound (TCD) are associated with the cerebrovascular responses measured by Magnetic Resonance (MR) imaging.

Official Title
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Brain Blood Flow Response to Hypercapnia in Healthy Adults: The Effect of Age and Sex

Conditions
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Healthy, Aging

Intervention / Treatment
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* Device: MRI
* Device: TCD


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Between 20-34 or 50-69 years Body mass index <34 kg/m2 Exclusion Criteria: Current smoker History or evidence of: hepatic disease, renal disease, hematological disease, peripheral vascular disease, stroke/neurovascular disease, diabetes, hypertension Part of a vulnerable population (e.g. pregnant women, prisoner, individuals lacking capacity to consent, etc.) Older females only: subject is not post-menopausal

Ages Eligible for Study
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Minimum Age: 20 Years
Maximum Age: 64 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Healthy young women<br>Healthy young women between the age of 20-34 years. | Device: MRI<br>* Participants will undergo a MRI scan while two stepwise CO2 elevations are applied to the participant by adding fractional concentration of inspired CO2 (FICO2) at 4% and 6% each time. The end tidal CO2 (PetCO2) will be elevated and maintained constant for a few minutes at each target level. Breath-by-breath changes in respiratory rate and PetCO2 will be measured.<br>* Other names: Magnetic Resonance Imaging;Device: TCD<br>* Participants will undergo a TCD scan while two stepwise CO2 elevations are applied to the participant by adding fractional concentration of inspired CO2 (FICO2) at 4% and 6% each time. The end tidal CO2 (PetCO2) will be elevated and maintained constant for a few minutes at each target level. Breath-by-breath changes in respiratory and PetCO2 will be measured.<br>* Other names: Transcranial Doppler Ultrasound;|
| Healthy young men<br>Healthy young men between the age of 20-34 years. | Device: MRI<br>* Participants will undergo a MRI scan while two stepwise CO2 elevations are applied to the participant by adding fractional concentration of inspired CO2 (FICO2) at 4% and 6% each time. The end tidal CO2 (PetCO2) will be elevated and maintained constant for a few minutes at each target level. Breath-by-breath changes in respiratory rate and PetCO2 will be measured.<br>* Other names: Magnetic Resonance Imaging;Device: TCD<br>* Participants will undergo a TCD scan while two stepwise CO2 elevations are applied to the participant by adding fractional concentration of inspired CO2 (FICO2) at 4% and 6% each time. The end tidal CO2 (PetCO2) will be elevated and maintained constant for a few minutes at each target level. Breath-by-breath changes in respiratory and PetCO2 will be measured.<br>* Other names: Transcranial Doppler Ultrasound;|
| Healthy older women<br>Healthy older women between the age of 50-64 years. | Device: MRI<br>* Participants will undergo a MRI scan while two stepwise CO2 elevations are applied to the participant by adding fractional concentration of inspired CO2 (FICO2) at 4% and 6% each time. The end tidal CO2 (PetCO2) will be elevated and maintained constant for a few minutes at each target level. Breath-by-breath changes in respiratory rate and PetCO2 will be measured.<br>* Other names: Magnetic Resonance Imaging;Device: TCD<br>* Participants will undergo a TCD scan while two stepwise CO2 elevations are applied to the participant by adding fractional concentration of inspired CO2 (FICO2) at 4% and 6% each time. The end tidal CO2 (PetCO2) will be elevated and maintained constant for a few minutes at each target level. Breath-by-breath changes in respiratory and PetCO2 will be measured.<br>* Other names: Transcranial Doppler Ultrasound;|
| Healthy older men<br>Healthy older men between the age of 50-64 years. | Device: MRI<br>* Participants will undergo a MRI scan while two stepwise CO2 elevations are applied to the participant by adding fractional concentration of inspired CO2 (FICO2) at 4% and 6% each time. The end tidal CO2 (PetCO2) will be elevated and maintained constant for a few minutes at each target level. Breath-by-breath changes in respiratory rate and PetCO2 will be measured.<br>* Other names: Magnetic Resonance Imaging;Device: TCD<br>* Participants will undergo a TCD scan while two stepwise CO2 elevations are applied to the participant by adding fractional concentration of inspired CO2 (FICO2) at 4% and 6% each time. The end tidal CO2 (PetCO2) will be elevated and maintained constant for a few minutes at each target level. Breath-by-breath changes in respiratory and PetCO2 will be measured.<br>* Other names: Transcranial Doppler Ultrasound;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Middle Cerebral Artery Blood Flow Measurement | Utilize the TCD and MR imaging to measure middle cerebral artery blood flow in the brain while the participant is at rest. | 75 minutes | 
| Middle Cerebral Artery Blood Flow Reactivity to Hypercapnia | Utilize the TCD and MR imaging to measure middle cerebral artery blood flow reactivity to hypercapnic gas. | 75 minutes | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Magnetic Resonance Imaging, Transcranial Doppler Ultrasound, Hypercapnia