Are Alzheimer’s disease and stroke related?

Alzheimer’s Disease and stroke are common pathologies of aging and their frequent co-occurrence has been recognized. Alzheimer’s disease is one of the leading causes of degenerative dementia and stroke also predisposes to vascular dementia. Recent studies have shown vascular-degenerative picture to be more common among individuals with dementia.

Stroke

Stroke is the acute condition characterized by reduction or interruption of blood supply to the tissues of the brain. This results in the rapid death of brain cells. Stroke is a medical emergency and timely treatment is vital in reducing deaths and related complications such as paralysis, pain, memory loss, loss of speech, etc.

Warning signs and symptoms

Identification of early symptoms and seeking immediate help is the key to effective stroke management. Some of the most symptoms related to stroke include

• Numbness and paralysis of legs, face, or hands, especially on one side of the body
• Difficulty in speaking and understanding other’s words and confusion
• Trouble walking or loss of balance
• Vision problems
• Headache

Types of stroke

• Ischemic Stroke – When blood flow through the artery that supplies oxygen rich blood to brain becomes blocked.
• Haemorrhagic Stroke – When the artery in the brain leaks blood or ruptures.
• Transient Ischemic attack – A temporary decrease in blood supply to part of the brain (about 5 mins)

Risk factors

The risk factors of stroke include

• Progressing age
• Obesity
• Alcohol or substance abuse
• Physical inactivity
• Hypertension, diabetes or high cholesterol
• Smoking
• Sleep disorders
• Preexisting heart conditions
• COVID-19 infection or brain infections
• Family history of stroke

Alzheimer’s disease

Alzheimer’s disease is a progressive neurodegenerative (destruction of the nervous system) disorder that destroys memory.

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Signs and symptoms

The most common symptoms include forgetfulness, difficulty with understanding and decision making.

The other symptoms are inability to recognize things, difficulty with calculations, way finding difficulty, behavioral and personality changes with mood disturbances.

At later stages full blown dementia sets in leading to significant reduction in patients’ quality of life.

Cause

The exact cause of Alzheimer’s disease is not known. At the initial stage, the disease affects the parts of the brain that are responsible for memory. However, as the disease progresses, there is an effect on the areas related to behaviour, reasoning, and language.

Cellular and molecular changes occur in the brain during Alzheimer’s disease. Chemicals, especially amyloid precursor proteins, are present in the brain that performs several vital functions. In Alzheimer’s disease, this protein breaks down into smaller proteins known as beta-amyloid. These proteins, especially beta-amyloid 42, are toxic to neurons. The beta-amyloids accumulate and form amyloid plaques around brain cells and interfere in functioning. The other protein is called tau protein, deposits of which form tangles within brain cells.

Also Read: Your parents can lose these memories if they have Alzheimer’s

Risk factors

The risk factors of Alzheimer’s disease include

• Progressing age
• Birth conditions such as Down syndrome
• Family history and genetics
• Cerebrovascular risk factors – smoking, obesity, diabetes mellitus and high blood pressure and cholesterol levels
• People with traumatic brain injuries are at risk of Alzheimer’s disease, and the risk increases with multiple injuries
• Sedentary lifestyle

How are stroke and Alzheimer’s disease connected?

Both stroke and Alzheimer’s disease are neurological disorders and have many common risk factors such as progressing age, physical inactivity, diabetes, hypertension, smoking, alcohol abuse etc. Many studies have demonstrated that patients with a history of stroke have a high risk of developing Alzheimer’s disease in future.

Such vascular risk factors and stroke increase may increase chronic inflammation, cerebral hypoperfusion, alter tau protein phosphorylation or increase amyloid beta protein precursor expression and processing which leads to neurodegeneration and cell death leading to with Alzheimer’s Disease.

Similarly, many researchers have shown increased risk of stroke in Alzheimer’s disease. Patients with AD dementia have higher risk of intra-cerebral hemorrhage, while there is no difference in the incidence of ischemic stroke in AD which is a more common type of stroke. Accumulation of amyloid Beta in cerebral blood vessels destroys the integrity of blood vessels which leads to increase in risk of hemorrhage in AD.

To translate in numbers and percentages, having stroke doubles the risk of dementia. Approximately 30% of stroke survivors develop post-stroke dementia.  Incidence of new onset dementia after stroke increases from 7% after 1^st year to 48% after 25 years.

Stroke and Alzheimer’s disease have many common risk factors and thus cutting down on these risk factors can help to prevent both. About 90% of the strokes are preventable and preventing stroke can help to cut down the risk of related dementia in more than one-third of the cases.

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Importance of preventing stroke to prevent dementia

Preventing stroke can help to cut down the risk of Alzheimer’s disease significantly. Some important measures to prevent stroke include:

• Managing underlying conditions such as high blood pressure, diabetes and high cholesterol levels with proper medicines and regular doctor visits
• Maintain a healthy weight
• Healthy eating and regular physical exercising
• Quitting smoking, drugs and alcohol

The last word

Many modifiable risk factors of stroke such as uncontrolled hypertension, diabetes mellitus, dyslipidemia, smoking, alcohol, obesity etc can increase the risk of Alzheimer’s disease and post stroke dementia by many folds. Public awareness about stroke, its warning signs and symptoms and effective management of these risk factors through lifestyle changes and medications can help to reduce the incidence of stroke and Alzheimer’s disease significantly.