Stroke And Alzheimer's: A Common Cause Of Death?

Alzheimer's disease is a multifactorial neurodegenerative disease characterised by memory loss, cognitive impairment, and the progressive degeneration of behavioural and functional capacities. Alzheimer's disease accounts for over 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 the blood supply to the brain is interrupted, resulting in a reduced oxygen supply to neurons.

People who have had a stroke have a far greater risk of developing dementia than people who have not. About a quarter of people who have had a stroke will go on to develop signs of dementia. This is because strokes can cause additional damage to brain regions previously unaffected by dementia.

However, the risk of stroke in patients with Alzheimer's disease is not clear. Some studies suggest that patients with Alzheimer's disease are more likely to have a hemorrhagic stroke, but not an ischemic stroke, compared to non-Alzheimer's controls with similar risk profiles. Other studies suggest that the risk of ischemic stroke in patients with Alzheimer's disease is increased by the greater burden of cerebral small vessel disease and atherosclerosis, which are risk factors for both Alzheimer's disease and stroke.

Alzheimer's disease and stroke often coexist

Alzheimer's disease (AD) and stroke often coexist, but subclinical cerebrovascular changes may begin many years before the manifestation of a clinical stroke. Decline in cognitive functions could reflect the degree of underlying cerebrovascular insults that occur along the natural history of either condition.

A stroke occurs when the blood supply to the brain is cut off or interrupted, resulting in reduced oxygen supply to neurons. This interruption is commonly caused by a clot blocking a blood vessel (ischemic stroke) or by a burst blood vessel (hemorrhagic stroke). Ischemic strokes account for 87% of all strokes worldwide, while hemorrhagic strokes account for 13%.

Vascular dementia is a general term describing problems with reasoning, planning, judgment, memory, and other thought processes caused by brain damage from impaired blood flow to the brain. It is the second most common form of dementia after Alzheimer's disease. Vascular dementia may be preventable, but only if the underlying vascular disease (such as hypertension) is recognized and treated early.

People who have had a stroke have a far greater risk of developing dementia than people who have not. About one in four people who have had a stroke will go on to develop signs of dementia within three to six months. However, strokes do not always cause vascular dementia, and whether a stroke affects cognitive function depends on its severity and location.

Compared with non-AD controls with similar risk profiles, patients with AD had a relative risk of 1.42 for hemorrhagic stroke and 1.15 for ischemic stroke. The incidence rate of hemorrhagic stroke was 3.41 per 1,000 person-years among patients with AD and 2.23 among non-AD controls. In contrast, the incidence rate of ischemic stroke was 13.98 among AD cases and 12.12 among non-AD controls.

In summary, Alzheimer's disease and stroke often coexist, and people with Alzheimer's disease are at an increased risk of both hemorrhagic and ischemic strokes. The risk of developing vascular dementia after a stroke depends on various factors, including the severity and location of the stroke, as well as the presence of underlying vascular diseases.

Cerebral amyloid angiopathy is associated with an increased risk of intracerebral haemorrhage in Alzheimer's patients

Cerebral amyloid angiopathy (CAA) is a cerebrovascular disorder caused by the accumulation of amyloid-beta (Aβ) in the walls of the arterioles and capillaries within the leptomeninges and in the penetrating vessels of the cerebral and cerebellar cortex. CAA is associated with an increased risk of intracerebral haemorrhage in patients with Alzheimer's disease. CAA is often associated with Alzheimer's disease and can result in recurrent lobar haemorrhages. CAA is a recognised cause of cerebral haemorrhage in elderly persons, in the absence of hypertension or coagulopathy. The haemorrhages are lobar, occurring in the cerebral cortex or subcortical white matter. Recurrence of lobar haemorrhage is more likely if the individual possesses the apolipoprotein-ε4 or ε2 allele. CAA is a frequent incidental finding, found on screening gradient-recalled echo imaging in up to 16% of asymptomatic elderly patients. The risk of intracerebral haemorrhage in patients with Alzheimer's disease is higher than in non-Alzheimer's disease controls with similar risk profiles.

People with Alzheimer's are more vulnerable to complications associated with cerebrovascular diseases

The nature of AD progression and its poor prognosis impose extra challenges to monitor and treat cerebrovascular complications in the AD population. Investigations to date focused on the risk of AD in patients with an established stroke diagnosis, with a broad consensus on the increased dementia risk after stroke. However, evidence on the risk in the opposite direction (i.e., the risk of stroke occurrence after AD diagnosis) is sparse, with discordant results.

People with AD are likely at a higher risk of hemorrhagic but not ischemic stroke. The increased risk of hemorrhagic stroke in patients with AD is possibly driven by the biological association of AD with cerebral amyloid angiopathy. CAA is associated with thinning of the endothelial cytoplasm, loss of pericytes, and changes in endothelial proteins that reduce the ability of the blood-brain barrier to compensate for leaks. Furthermore, microbleeds identified on MRI are prevalent in patients with AD, although the mechanism remains unclear. CAA and microbleeds are common in patients with AD and have been established as risk factors for intracerebral hemorrhage (ICH) and sporadic hemorrhagic stroke in the elderly and therefore possibly together play a key role in ICH onset in patients with AD.

The findings of the present report suggest no increased risk of ischemic stroke in patients with AD compared with non-AD controls. Among studies included, 1 investigation based on the Taiwan's National Health Insurance Research Database reported a high risk of ischemic stroke in patients with AD. This observation could be explained by a greater burden of cerebral small vessel disease and atherosclerosis in patients with AD that are risk factors for both AD and stroke.

People who have had a stroke have a far greater risk of developing dementia than people who have not had a stroke. About 1 in 4 people who have had a stroke will go on to develop signs of dementia. Almost a quarter of people who have had a stroke will go on to develop dementia after about three to six months.

Vascular dementia is the second most common form of dementia after Alzheimer's disease

Vascular dementia is the second most common form of dementia, after Alzheimer's disease. It is a general term describing problems with reasoning, planning, judgement, memory, and other thought processes caused by brain damage from impaired blood flow to the brain. Vascular dementia can develop after a stroke blocks an artery in the brain, but strokes do not always cause vascular dementia. The risk of vascular dementia increases with the number of strokes that occur over time.

Vascular dementia symptoms vary depending on the part of the brain where blood flow is impaired. Symptoms often overlap with those of other types of dementia, especially Alzheimer's disease. However, the most significant symptoms of vascular dementia tend to involve speed of thinking and problem-solving rather than memory loss.

Vascular dementia can result from other conditions that damage blood vessels and reduce circulation, depriving the brain of vital oxygen and nutrients. These conditions include:

• Stroke (infarction) blocking a brain artery
• Brain haemorrhage caused by high blood pressure
• Narrowed or chronically damaged brain blood vessels due to wear and tear associated with ageing, high blood pressure, abnormal ageing of blood vessels, or diabetes

The risk factors for vascular dementia are similar to those for heart disease and stroke, including increasing age, high blood pressure, high cholesterol, diabetes, smoking, and obesity.

About 1 in 4 people who have had a stroke will go on to develop signs of dementia

Stroke-related dementia, or vascular dementia, is a general term describing problems with reasoning, planning, judgment, memory, and other thought processes caused by brain damage from impaired blood flow to the brain. About 1 in 4 people who have had a stroke will go on to develop signs of dementia.

Vascular dementia is the second most common type of dementia, after Alzheimer's disease. It occurs when the brain suffers an injury due to decreased blood flow.

The symptoms of vascular dementia are similar to those of other types of dementia. However, in the early days following a stroke, it can be difficult to distinguish dementia from the symptoms of the stroke itself. Some symptoms of dementia after a stroke include:

• New or worsening memory impairments, such as trouble remembering names or recent events
• Problems with decision-making, such as the inability to make good decisions or follow directions
• Confusion, such as frequently getting lost
• Problems with self-care, such as difficulty bathing or getting dressed
• Speech issues such as difficulty speaking or understanding speech
• Changes in mood or personality, such as depression, aggression, or anxiety

Vascular dementia is most common in older people, who are more likely than younger people to have vascular diseases. It is more common in men than in women.

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