Alzheimer's And Stroke: What's The Link?

Alzheimer's disease is a multifactorial neurodegenerative disease characterised by memory loss, cognitive impairments, and the progressive degeneration of behavioural and functional capacities. It accounts for more than 80% of dementia cases worldwide in people over 65.

Strokes are the second leading cause of death and the third leading cause of disability-adjusted life-years worldwide. They occur when blood flow to the brain is interrupted, causing neurons to be deprived of oxygen.

Research has shown that stroke is a major factor in vascular dementia, which is the most serious dementing illness after Alzheimer's disease, accounting for about 10% of all dementia cases.

Strokes can cause vascular dementia, and about a quarter of people who have had a stroke will go on to develop dementia within three to six months. However, not everyone who has a stroke will experience vascular dementia.

How does a stroke increase the risk of vascular dementia?

Vascular dementia is caused by brain damage from impaired blood flow to the brain. A stroke can block an artery in the brain, cutting off the blood supply and causing vascular dementia. However, not all strokes cause vascular dementia, and the risk depends on the severity and location of the stroke.

The risk of vascular dementia increases with the number of strokes that occur over time. This is because the brain damage caused by strokes can affect a person's thinking and reasoning abilities. Factors that increase the risk of heart disease and stroke, such as diabetes, high blood pressure, high cholesterol, and smoking, also raise the risk of vascular dementia.

Vascular dementia can also be caused by other conditions that damage blood vessels and reduce circulation, depriving the brain of oxygen and nutrients. These conditions include:

• Brain haemorrhage, often caused by high blood pressure or the buildup of protein in small blood vessels.
• Narrowed or chronically damaged brain blood vessels due to ageing, high blood pressure, abnormal ageing of blood vessels, or diabetes.
• Atrial fibrillation, an irregular heartbeat that can cause blood clots.

Additionally, the risk of vascular dementia increases with age, with the disorder being rare before the age of 65 and rising substantially by the age of 90.

What are the different types of vascular dementia?

There are several types of vascular dementia, all of which are caused by problems with blood supply to parts of the brain, which then become damaged. The most common type is subcortical vascular dementia, which is caused by diseases of the very small blood vessels that lie deep in the brain. Over time, these blood vessels can develop thick walls and become stiff and twisted, so blood cannot travel through them easily. The parts of the brain supplied by these blood vessels become starved of oxygen and nutrients and eventually stop working altogether.

Multi-infarct dementia is caused by a series of smaller strokes or transient ischaemic attacks (TIAs). TIAs are similar to strokes but the symptoms last only a short time and tend to get better by themselves.

Stroke-related dementia is caused by a stroke that suddenly cuts off the blood supply to a part of the brain. With most strokes, a blood vessel in the brain becomes narrowed and is blocked by a clot. Sometimes, it is because the vessel bursts and bleeds into the brain, but this is much less common.

Single-infarct dementia is another type of vascular dementia that typically happens when someone has one severe ischemic stroke.

How is vascular dementia treated?

Vascular dementia is caused by a lack of blood flow to the brain. While there is currently no cure, treatment can help to slow down its progression and prevent further damage to the brain.

The main goal of vascular dementia treatment is to address the underlying conditions that affect blood flow to the brain. This can help to reduce the risk of further damage to brain tissue. Treatment may include:

• Medication to manage blood pressure, cholesterol, diabetes, and problems with blood clotting
• Lifestyle changes, such as a healthy diet, physical activity, quitting smoking, and reducing alcohol consumption
• Surgery to improve blood flow to the brain, such as carotid endarterectomy, angioplasty, and stenting
• Medication to treat the symptoms of dementia, such as cholinesterase inhibitors or antidepressants

Before treatment begins, a person's current and future health and social care needs will be assessed, and a care plan will be created. This plan will identify areas where the person may need help, such as support to remain independent, changes to their home to make it easier to live in, and financial assistance.

What is the outlook for people with vascular dementia?

Vascular dementia is a progressive disease with no cure. It is caused by reduced blood flow to the brain, which damages and kills brain cells. The condition tends to get worse over time, though treatment can sometimes slow it down.

People with vascular dementia will eventually need a high level of care as their mental and physical abilities decline. They may initially be cared for at home by family members, but will likely need more specialised care as the disease progresses.

Vascular dementia can shorten life expectancy, though this is highly variable, and many people live for several years with the condition. Treatment can help slow down the progression of the disease and improve quality of life.

What are the risk factors for vascular dementia?

Vascular dementia is caused by conditions that interrupt the flow of blood and oxygen supply to the brain and damage blood vessels in the brain. The risk factors for vascular dementia are similar to those for heart disease and stroke. These include:

• Increasing age. The risk of vascular dementia rises as you grow older. The disorder is rare before age 65, and the risk rises substantially by your 90s.
• History of heart attacks, strokes or ministrokes. The brain damage that occurs with a stroke or a ministroke may increase your risk of developing dementia.
• Abnormal aging of blood vessels (atherosclerosis). This condition occurs when deposits of cholesterol and other substances (plaques) build up in your arteries and narrow your blood vessels.
• High cholesterol. Elevated levels of low-density lipoprotein (LDL), the "bad" cholesterol, are associated with an increased risk of vascular dementia.
• High blood pressure. When your blood pressure's too high, it puts extra stress on blood vessels everywhere in your body, including your brain.
• Diabetes. High glucose levels damage blood vessels throughout your body. Damage in brain blood vessels can increase your risk of stroke and vascular dementia.
• Smoking. Smoking directly damages your blood vessels, increasing your risk of atherosclerosis and other circulatory diseases, including vascular dementia.
• Obesity. Being overweight is a well-known risk factor for vascular diseases in general, and therefore, presumably increases your risk of vascular dementia.
• Atrial fibrillation. In this abnormal heart rhythm, the upper chambers of your heart begin to beat rapidly and irregularly, out of coordination with your heart's lower chambers. Atrial fibrillation increases your risk of stroke because it causes blood clots to form in the heart that can break off and go to the brain blood vessels.
• Sleep apnoea. This is a common health problem where a person stops breathing for a few seconds or minutes during sleep. This can cause small blood clots to form in the brain that go unnoticed. These greatly increase the risk of high blood pressure, stroke, heart attacks and vascular dementia.
• Cerebral amyloid angiopathy (CAA). This is a type of vascular disease that damages the small arteries of the outer regions of the brain. This causes the blood vessels in that part of the brain to become leaky and prone to bleeding.
• Cardiovascular conditions. People who have problems with their heart and blood circulation, such as high blood pressure or heart disease, have a higher risk of developing vascular dementia. This is because these conditions increase the chances of a clot or bleed happening in the blood vessels in the brain.
• Sex. Men are at slightly higher risk of developing vascular dementia than women.

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