High blood pressure (BP) in midlife is predictive of Alzheimer's disease (AD) in later life. Similarly, reductions in BP are associated with protection against AD. Treatment with antihypertensive medications, specifically angiotensin converting enzyme inhibitors (ACE-I) such as ramipril, is associated with up to a 55% reduction in the prevalence of AD, suggesting a potentially promising role for ACE-I in the prevention of AD. It is unknown however 1) whether ACE-Is will have the same effect on CSF Aβ levels in humans as in animal models 2) whether ACE-Is induce changes associated with vascular function (i.e. levels of CSF angiotensin converting enzyme (ACE) and peripheral endothelial function) and 3) whether there are interactions between ACE-I-induced changes in CSF Aβ, CSF ACE and indices of vascular function.