Alzheimer's Disease

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Risk Factors

The risk for Alzheimer's disease increases with each decade of adult life. People with a family history of Alzheimer's have a greater risk, implying that a genetic factor is involved. A clear inherited pattern of AD exists in less than 10% of cases. Some involve a mutation of the gene for the protein APP, found on chromosome 21. Nearly all people with Down's syndrome (trisomy 21) who live into their 40s develop the disease. Others involve a defect on chromosome 14. The gene for the protein Apo E, found on chromosome 19, is a risk factor that may be involved in modifying the age of onset.

Untreated chronic high blood pressure (hypertension) has been identified as a risk factor for loss of mental function in older people. Treatment reduces the risk. Adults who have had head injuries are three times more likely to develop Alzheimer's disease.

It is thought that gender plays a role because several studies suggest that women are afflicted with Alzheimer's disease more often than men. However, the evidence is inconsistent and some studies report that the disease is more prevalent in men. Therefore, more research is needed to obtain conclusive evidence regarding prevalence in gender.

Causes

Genetic factors are known to play a role in some cases of Alzheimer's. The APP gene found on chromosome 21 is implicated in the occurrence of AD in Down's syndrome patients who survive beyond 40 years. Some families with a history of early-onset AD have a mutation on the APP gene and others have a mutation in the presenilin-1 gene (PS-1) found on chromosome 14. Another gene, the Apo E gene on chromosome 19, also has been implicated in the disease. Apo E is a protein found with beta amyloid in neuritic plaques.

It is not known whether the characteristic neuritic plaques and neurofibrillary tangles are the cause or the result of the disease process.

Signs and Symptoms

Early symptoms, such as memory loss, may be attributed to the forgetfulness associated with ageing. Gradually, the loss of cognitive function disrupts the patient's ability to perform common daily activities, such as paying bills, driving, and housekeeping. Some people remain unaware of their symptoms, while others are painfully aware of the fact that they are losing mental function.

Symptoms of Alzheimer's disease include the following:

• Apraxia (inability to perform physical tasks such as dressing, eating)
• Aphasia (loss of ability in comprehension of spoken or written language)
• Delusions
• Easily lost and confused
• Inability to learn new mental tasks
• Loss of judgment, reason, and cognitive abilities
• Loss of inhibitions and belligerence
• Social withdrawal
• Visual hallucinations

In end-stage Alzheimer's disease, patients may become bedridden and need help with eating and getting out of bed to use the bathroom. Patients also may experience convulsions and seizures and may become incontinent.

Complications
Depression is common in patients with Alzheimer's disease, especially during the earlier stages when they may be aware of losing mental functions.

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