ALZHEIMER'S DISEASE
Definition
Alzheimer's disease (AD) is the most common cause of dementia in the elderly, accounting for approximately 60% of cases of dementia. AD is defined as memory loss with at least one other area of cognitive impairment (e.g., language, attention, orientation, self-monitoring, judgment, motor skill, inability to perform daily activities). Memory loss usually begins at about age 65 and slowly progresses to severe impairment over 8 to 10 years, but it may present earlier and advance at a faster or slower rate; early onset of Alzheimer's disease heralds a particularly aggressive form.
Typically, language deficits are prominent, including those in word finding (especially nouns), comprehension, repetition, and fluency. Social graces, which may remain surprisingly intact for years, eventually deteriorate to a loss of inhibition, with periods of aggression or withdrawal. Personality and behavioural changes as well as problems in judgment occur with increasing severity. Death usually occurs from malnutrition, heart disease, or infection. Approximately 20% of cases of Alzheimer's are actually attributable to another disease process; definitive diagnosis can only be confirmed at time of autopsy.
Aetiology / Risk Factors
Major causative factors and risk factors that can contribute to the incidence of Alzheimer’s disease include the following:
- Family history
- Advanced age (20% to 40% with fully developed symptoms of AD are over age 85)
Female > male—results of studies are not conclusive, however; the greater incidence in women may be related to their tendency to greater longevity
Longstanding hypertension
History of head trauma—association is not definitive
Lower educational level—association is not definitive, but may be related to the observation that learning is necessary to stimulate growth of neurons
Trisomy 21 (Downs syndrome)
Elevated homocysteine
Western diet and lifestyle (less common in Asia and Africa, increases as people move to west)
Exposure to electromagnetic fields (unproven)
Other factors speculated to contribute to the development of AD include infections (e.g., herpesvirus 1 or
Chlamydia pneumonia and, possibly, prions)
Symptoms and Signs
Common signs and symptoms of Alzheimer’s disease include the following:
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Memory loss—eventually includes loss of personal information and inability to recognise family (CT or MRI may distinguish AD from multi-infarct dementia or other causes)
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Diminished concentration
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Aphasia—language deficits in the areas of fluency, comprehension, and word naming/finding; the latter may help differentiate from normal signs of aging
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Temporal and spatial disorientation—may lead to aimless wandering
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Muscle rigidity and shuffling gait—resembles Parkinson's disease without a tremor
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Depression
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Accusatory behaviours
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Hallucinations, delusions, psychosis; the beliefs expressed are often quite concrete (e.g., false accusations of spousal infidelity, accusing a friend of stealing, being frightened of their own image)
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Aggression, agitation, anxiety, restlessness
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Withdrawal, apathy, and social passivity may alternate with belligerence and loss of inhibitions
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Insight ranges from completely unaware (agnosia), to extremely insightful (which contributes to frustration and anxiety)
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Insomnia or disturbances in sleep/wake patterns
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Weight loss
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Incontinence
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Myoclonic jerks or generalised seizures
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Diffuse atrophy of the cerebral cortex; secondary enlargement of the ventricular system; loss of volume in the hippocampus, detected by MRI