Alzheimer’s disease is a neurological disorder in which the death of brain cells causes memory loss and cognitive decline. A neurodegenerative type of dementia, the disease starts mild and gets progressively worse.
What causes Alzheimer’s disease?
Like all types of dementia, Alzheimer’s is caused by brain cell death.3 It is a neurodegenerative disease, which means there is progressive brain cell death that happens over a course of time.
The total brain size shrinks with Alzheimer’s – the tissue has progressively fewer nerve cells and connections While they cannot be seen or tested in the living brain affected by Alzheimer’s disease, postmortem/autopsy will always show tiny inclusions in the nerve tissue, called plaques and tangles.
- Plaques are found between the dying cells in the brain – from the build-up of a protein called beta-amyloid (you may hear the term “amyloid plaques”).
- The tangles are within the brain neurons – from a disintegration of another protein, called tau.
- Unavoidable risk factors
- Age – the disorder is more likely in older people, and a greater proportion of over-85-year-olds have it than of over-65s.2
- Family history (inheritance of genes) – having Alzheimer’s in the family is associated with higher risk. This is the second biggest risk factor after age.7
- Having a certain gene (the apolipoprotein E or APOE gene) puts a person, depending on their specific genetics, at three to eight times more risk than a person without the gene.6 Numerous other genes have been found to be associated with Alzheimer’s disease, even recently (see developments below).7
- Being female (more women than men are affected).
Potentially avoidable or modifiable factors
- Factors that increase blood vessel (vascular) risk – including diabetes, high cholesterol and high blood pressure. (These also increase the risk of stroke, which itself can lead to another type of dementia.)
- Low educational and occupational attainment.
- Prior head injury. (While a traumatic brain injury does not necessarily lead to Alzheimer’s, some research links have been drawn, with increasing risk tied to the severity of trauma history.)8
- Sleep disorders (the breathing problem sleep apnea, for example).
- Estrogen hormone replacement therapy.
Signs and symptoms
- 1. Worsened ability to take in and remember new information, for example:
- “Repetitive questions or conversations
- Misplacing personal belongings
- Forgetting events or appointments
- Getting lost on a familiar route.”
2. Impairments to reasoning, complex tasking, exercising judgment:
- “Poor understanding of safety risks
- Inability to manage finances
- Poor decision-making ability
- Inability to plan complex or sequential activities.”
3. Impaired visuospatial abilities (but not, for example, due to eye sight problems):
- “Inability to recognize faces or common objects or to find objects in direct view
- Inability to operate simple implements, or orient clothing to the body.”
4. Impaired speaking, reading and writing:
- “Difficulty thinking of common words while speaking, hesitations
- Speech, spelling, and writing errors.”
5. Changes in personality and behavior, for example:
- Out-of-character mood changes, including agitation; less interest, motivation or initiative; apathy; social withdrawal
- Loss of empathy
- Compulsive, obsessive or socially unacceptable behavior.
Once the number and severity of these example symptoms confirm dementia, the best certainty that they are because of Alzheimer’s disease is given by:
- A gradual onset “over months to years” rather than hours or days (the case with some other problems)
- A marked worsening of the individual person’s normal level of cognition in particular areas.11
The most common presentation marking Alzheimer’s dementia is where symptoms of memory loss are the most prominent, especially in the area of learning and recalling new information. But the initial presentation can also be one of mainly language problems, in which case the greatest symptom is struggling to find the right words.11
If visuospatial deficits are most prominent, meanwhile, these would include inability to recognize objects and faces, to comprehend separate parts of a scene at once (simultanagnosia), and a type of difficulty with reading text (alexia). Finally, the most prominent deficits in “executive dysfunction” would be to do with reasoning, judgment and problem-solving.11
Stages of Alzheimer’s disease
The progression of Alzheimer’s can be broken down into three basic stages:12
- Preclinical (no signs or symptoms yet)
- Mild cognitive impairment
The Alzheimer’s Association has broken this down further, describing seven stages along a continuum of cognitive decline based on symptom severity – from a state of no impairment, through mild and moderate decline, and eventually reaching “very severe decline.”
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