Cerebrovascular disease is a group of brain dysfunctions related to disease of the blood vessels supplying the brain. Hypertension is the most important cause; it damages the blood vessel lining, endothelium, exposing the underlying collagen where platelets aggregate to initiate a repairing process which is not always complete and perfect. Sustained hypertension permanently changes the architecture of the blood vessels making them narrow, stiff, deformed, uneven and more vulnerable to fluctuations in blood pressure. A fall in blood pressure during sleep can then lead to a marked reduction in blood flow in the narrowed blood vessels causing ischemic stroke in the morning...