Cerebral thrombosis is a common disease in the elderly. Its occurrence is not only related to the progress of hypertension and atherosclerosis, but also closely related to the increase of blood viscosity in the elderly. In fact, the higher the blood viscosity of the elderly, the more likely cerebral thrombosis occurs. Blood flowing in human blood vessels is like a river, the faster the flow, the less precipitation; conversely, the slower the flow, the more precipitation. The increase of blood viscosity will inevitably lead to the slowing down of blood flow, and the platelets, cholesterol, fibrin and other substances in the blood will be precipitated on the blood vessel wall, and over time, the precipitates will accumulate more and more, and if combined with hypertension, arteriosclerosis and other diseases, it will lead to cerebral thrombosis. Research has confirmed that the viscosity of human blood is constantly changing throughout the day and has its own certain pattern: the highest blood viscosity from 4:00 a.m. to 8:00 a.m., then gradually decreases to reach the lowest point in the early morning, and then gradually rises to reach the peak again in the morning. This regular fluctuation is more prominent in the elderly. In addition, the onset of cerebral thrombosis is usually between the morning and the morning, suggesting a relationship between increased blood viscosity and the occurrence of cerebral thrombosis. Another study has confirmed that when elderly people drink 200 ml of commercially available mineral water late at night, the blood viscosity does not increase but decreases in the morning. Therefore, it is generally believed that drinking water at night can lower blood viscosity, maintain smooth blood flow and prevent thrombosis. Of course, the cause of cerebral thrombosis is multifaceted, and the increase of blood viscosity is only one of the many factors, but at least it is certain that the habit of drinking water before bedtime will play a certain role in preventing the occurrence of cerebral thrombosis. Why does low blood pressure also cause cerebrovascular disease? 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. Clinical studies have proven that both high and low blood pressure can bring damage to blood vessels. When the blood pressure is too high, the cerebral blood vessels are congested and the pressure inside the blood vessels rises significantly, and when it exceeds the degree that the blood vessels can tolerate, it will rupture and bleed and cerebral hemorrhage will occur. While blood pressure is too low, it cannot make the blood vessels expand normally, the blood circulation volume decreases, the cerebral blood vessels spasm, making the brain tissue ischemia, hypoxia and infarction. 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. In our daily life, we often encounter this situation: 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 distorted 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.