It is common knowledge that high blood pressure can cause cerebrovascular disease, but it is often overlooked that low blood pressure can also cause cerebrovascular disease. In fact, cerebrovascular disease caused by low blood pressure is not uncommon. Low blood pressure does not allow the blood vessels to expand normally, which reduces the amount of blood circulation and cerebral vascular spasm, causing ischemia, hypoxia and infarction of brain tissue. In addition, the vascular pressure is too low, the lumen is relatively narrow, the blood flow is slow, easy to platelet aggregation, blood viscosity increases, and cerebral thrombosis occurs. It is often encountered that some people do not have high blood pressure or a history of hypertension, and they are fine before going to bed, but when they wake up early the next morning, they suddenly have a lopsided mouth and eyes, hemiplegia and aphasia. What is the reason for this? The main reason is that blood pressure is lower at night than during the day, and platelets, cholesterol, triglycerides and fibrin in the blood are easily deposited and blood flow is slow, which makes it easy to have insufficient blood supply to the brain, resulting in blockage of blood vessels and cerebrovascular disease. This shows that people with low blood pressure, especially the elderly, still have the possibility of ischemic cerebrovascular disease. Therefore, blood pressure should be regulated to keep it within the normal range in order to prevent the occurrence of cerebrovascular disease.