Alzheimer's disease

Dementia is a progressive decrease in cognitive capacity that usually appears in elderly adults. The most common form of dementia is Alzheimer's Disease (AD) which affects one fifth of the population of over 80 years old age.

Alzheimers Disease begins with the inability to recall recent events, while remembering events from the past, e.g. from childhood or youth, pose no difficulties to the patients. Upon disease progression, other cognitive problems appear, such as; difficulties with speech, people recognition, fine motor tasks, spatial orientation and solving abstract problems can develop as well. Additionally in late phases, confabulations, hallucinations and personality changes may appear. Alzheimers Disease can be properly diagnosed in the advanced stages through a series of simple mental tests.

Diagnosis

An important diagnostic criterion is the inability of an Alzheimer's patient to lead an independent life. In addition, memory loss must be present and other cognitive abilities affected. To date, there is no reliable laboratory test for diagnostic purposes available. Diagnosis can be suspected on the basis of results of simple cognitive tests, but psychological testing enables a more detailed appraisal of cognitive abilities. Imagining studies also aid in making the diagnosis. Serial magnetic resonance imaging shows progressive brain atrophy (brain shrinkage) which is most pronounced in the temporal regions of the brain.

Reasons for Alzheimer's disease development

The cause of disease in most cases remains unknown. If the patient's brain tissue is examined under a microscope, protein threads (neurofibrillary tangles) can be detected in the neurons. Protein accumulations (neuritic plaques) are dispersed throughout the brain. The changes are most pronounced in the temporal brain regions which is the area responsible for memory formation. It is not clear which entity is responsible for the reduction in cognitive abilities--the tangles, plaques or both. In addition, there are deficiencies of various chemical transmitters in the brain which are important for inter-neuronal communication. They are called neurotransmitters. Neurons communicate with each other by exchanging these substances and thereby passing information. In Alzheimer's disease, neurons that use the neurotransmitter acetylcholine are very much affected.

Prevention

Risk factors for Alzheimer's Disease include; age, gender, genetics, lifestyle and environment. Age is the most significant risk factor for Alzheimer's Disease. Women are at an increased risk of developing Alzheimer's Disease. Obviously, age, gender and genetics are all factors that we are unable to control. 

Intellectual activities such as playing chess, learning new languages, crossword puzzle solving and, above all, regular social interaction with family and friends are all very beneficial for they can somewhat slow down the progression of Alzheimer's disease and ameliorate its course. Moderate physical activity and pursuing sports is also recommended. Dancing is very beneficial as it requires one to acquire new movement skills and memorize dance steps, in addition to offering a chance to exercise and relax.

Effective prevention of Alzheimer's disease with medications is still not possible. 

In the past, a vaccine was researched that would remove neuritic plaques that form in the brain of Alzheimer's patients. Unfortunately, however, the trial had to be prematurely terminated as some of the patients got encephalitis and succumbed to it. Research is currently under way into the development of newer and cleaner vaccines.

Typically, signs of minor infarction are evident in the brain of Alzheimer's patients. Thus, it is important to treat hypertension, the increased cholesterol level and cardiac arrhythmia in old age. In addition, smoking cessation is much encouraged. All these are risk factors for a stroke that may further worsen the cognitive difficulties.

Therapy

Currently, the treatment for Alzheimer's disease is merely symptom management; medications that prevent acetylcholine breakdown are employed to this effect. Acetylcholine is a signalling substance used by the nerve cells for communication and is in severe shortage in the brains of Alzheimer's patients. The medications act to inhibit the action of acetylcholinesterase, the enzyme that normally breaks down acetylcholine; thus, the concentration of acetylcholine in the brain increases.

Unfortunately, these medications are not very effective. They can improve a patient's memory to some extent and facilitate contact with caretakers. Generally, medications can restore a patient’s mental state to about the same state that was in place 6 months prior to starting the medication.

A different mode of action is exhibited by the drug memantine which blocks glutamate receptors in the brain. Glutamate is a neurotransmitter that excites neurons. When memantine acts to block glutamate receptors, glutamate cannot bind to its receptors and thus cannot excite neurons. Memantine is approved for the treatment of moderate to severe forms of Alzheimer's dementia. A special group is comprised of medications that could prevent the development and progression of Alzheimer's disease. They act to block the enzymes beta-secretase and gamma-secretase, i.e. the enzymes that are responsible for the formation of plaques in the brain. Unfortunately, the recent clinical trials involving these drugs have been unsuccessful.

The search process for a successful drug for Alzheimer's disease is very intense. Worldwide there are currently over 200 medications for Alzheimer's disease in phase III of clinical trials. It is expected that a discovery of more successful medications will significantly slow down the progression of Alzheimer's disease or even prevent its appearance altogether.