Mechanisms of Impaired Brain Blood Flow With Aging

Inclusion criteria

• 18-29 or 55-79 years old

Exclusion criteria

• Pregnancy or breastfeeding;
• Blood chemistries indicative of abnormal renal, liver, thyroid and adrenal function (i.e., outside of normal reference range); estimated glomerular filtration rate using the MDRD prediction equation must be >60 ml/min/1.73 m2;
• Abnormal blood chemistry that is clinically relevant or any blood chemistry marker that is +/-2.5x the upper or lower limit;
• Lack of a suitable temporal window for cerebrovascular assessments;
• Current smoking;
• Chronic clinical diseases (e.g., coronary artery, peripheral artery, or cerebrovascular diseases, diabetes, chronic kidney disease, COPD);
• Major psychiatric disorder (e.g. Alzheimer's disease or other form of dementia, schizophrenia, bipolar disorder, major depression within past two years);
• Neurological or autoimmune conditions affecting cognition (e.g. Parkinson's disease, epilepsy, multiple sclerosis, head trauma with loss of consciousness greater than 30 min, large vessel infarct);
• Current medication use likely to affect CNS functions (e.g. long active benzodiazepines);
• Having past or present alcohol dependence or abuse, as defined by the American Psychiatry Association, Diagnostic and Statistical Manual of Mental Disorders;
• Body mass index (BMI) >40 kg/m2 (FMD measurements can be inaccurate in severely obese patients).