4  Maintain the Blood and Oxygen Supply to the Brain

Everything that is written and said about the prevention of heart disease or the prevention of stroke appears to be equally relevant to the prevention of dementia. These are presented as the following key points:
          Increase physical activity (covered in the previous chapter).
          Rebalance your diet.
          Keep your sugar low, avoid type 2 diabetes.
          Keep your cholesterol low.
          Stop smoking.
          Keep your blood pressure low.
          Keep your weight down.
          Find out if you have atrial fibrillation and get it treated.
          Check if you have had a transient ischaemic attack (TIA for short) the word ‘ischaemic’ being Greek for ‘without blood’.
Vascular dementia is caused by damage to the arteries of the brain and this damage is caused by the same risk factors that cause heart disease, because what is called heart disease is in fact disease of all the arteries, including the arteries of the brain. Therefore, the steps taken to reduce the risk of heart disease also reduce the risk of dementia. In addition, most of the people who have one of the different types of dementia, including those with a specific name such as Alzheimer’s disease, also have some disease in their arteries. This is because almost everyone in a modern, industrialized society has some degree of arterial disease; atherosclerosis is the name of the underlying disease process.
If a major artery is blocked or if the artery bursts the result is called a stroke and is usually made obvious by paralysis of one side of the body. Sometimes the blockage is small, temporary, and disappears after the patient experiences weakness, numbness or paralysis in the face, arm, or leg, slurred or garbled speech or difficulty understanding others, or blindness in one or both eyes, or double vision. This is called a transient ischaemic attack (TIA) or mini stroke. If the TIA happens in a part of the brain that controls other functions, some aspect of memory for example, then the event may pass without notice but if lots of little blockages occur the consequences are serious, vascular dementia.
Doctors have long suspected the fact that some people developed dementia because they had experienced lots of infarcts. Infarcts being small areas of dead tissue, killed by lack of blood supply. Each of these infarcts would have affected parts of the brain that did not control muscle movement and therefore did not cause any signs of weakness. They were too small to be seen until, that is, the development of magnetic resonance imaging (MRI), which is much more powerful than traditional X-rays. These allowed research radiologists, such as the team at the University of Edinburgh, led by Professor Joanna Wardlow, to demonstrate the presence of tiny flecks of white in the brains of people with dementia. This demonstrated that vascular dementia was a real entity. These tiny areas of damage were found everywhere in the brain. This demonstrated that vascular dementia was a real entity and is recognized as a contributor to small strokes and silent strokes.
The circulation system is like a central heating system. In a central heating system there is a boiler with pump; the heart is the pump in the circulation system. The pump in a central heating system circulates energy, produced by burning coal, oil, or gas in a boiler. In the body, the energy is produced from carbohydrates burned in all the tissues, with oxygen drawn in from the lungs and carried by the blood to the tissues through the arteries. Unlike the central heating system, the energy is not generated in the central boiler but in the tissues of the body, by the interaction between oxygen and carbohydrate. This happens everywhere, for example in the muscles. In the brain, any interruption in the flow of oxygen results in an interruption in the production of energy, and tissues which are starved of energy die.
There are three ways in which the circulation of blood to the brain tissue can be cut off. An artery may:
 
Become progressively furred up, just like a water pipe, by the development of a substance often described by pathologists as ‘porridgy’ in the walls of the artery. This process of narrowing the arteries is called atherosclerosis and is the result of several factors, one of which is inflammation.
 
Simply burst, usually due to a combination of high blood pressure, and the weakening of the artery wall that results from atherosclerosis.
 
Become blocked by a clot of blood that has developed in the heart and is then carried through arteries. These arteries become smaller and smaller until they are too small for the clot to pass through, causing it to stick there. This blocks the supply of oxygen to the part of the brain that depends on that artery for its oxygen supply. The reason a clot forms is usually if there is an irregular rhythm of the heart, a disorder called atrial fibrillation. If the clot is a big one, it will stick sooner, as arteries divide again and again into smaller and smaller branches. The result is a stroke, which may be fatal or paralyse half the body. If the clot is smaller it can cause one of the tiny infarcts that may not paralyse the nerves and muscles but will knock out part of the intellectual function of the brain.
Of course, atrial fibrillation, irregular beating of the pulse, is itself often the result of atherosclerosis of the blood vessels of the heart; arteries in the brain affected by high blood pressure are more likely to burst or become blocked.
Similarly, the risk factors for arterial disease overlap with one another. Several of these ideas were discussed in the previous chapters and overlap here. Though this time it is applied to arteries as opposed to just brain tissue.
Many of the twenty-first century health problems are the result of a combination of inactivity and diet. For example, type 2 diabetes is due to both reduced activity levels and increased calorie intake in most people. Similarly, hypercholesterolaemia, raised levels of cholesterol in the bloodstream, is also due to a combination of these two factors in most people. There are some people who have a genetic disorder which means that they have high levels of cholesterol no matter how active they are. Usually activity and diet are two sides of the coin, or like Yin and Yang, or interwoven like the warp and weft of Harris Tweed. Thus, we will consider diet and type 2 diabetes and raised levels of cholesterol in this chapter.
Raised levels of blood pressure occur not only as a result of obesity, but also from many other factors which we do not understand. Even lean people can have high blood pressure. So, for this reason we will consider blood pressure on its own, except to emphasize that keeping your weight down is a good way of preventing high blood pressure, and if high blood pressure has been diagnosed, of reducing the blood pressure. In summary, therefore, in this chapter we are going to consider several topics, but they do overlap and interrelate. When, however, a person develops one of these conditions they are often put on a pathway by their health service which makes it feel as if their condition, type 2 diabetes for example, is a separate condition, whereas it is part of a group of conditions that often occur together. 

so the risk of dementia can be reduced by keeping the blood and oxygen flowing
 
 
From
Increase your Brainability and Reduce Your Risk of Dementia 
By
Larry Chambers, Charles Alessi, and Muir Gray 
OUP 2022