What Is Alzheimer's Disease?

According to Harrison's Principles of Internal Medicine, dementia is a syndrome with many causes. The term is applied when a "deterioration in cognitive abilities impairs the previously successful performance of normal activities" in your daily life. Memory is the most common and most important cognitive ability that is lost.

The most common cause of dementia is Alzheimers disease (AD), making up 50% of all cases. The other 50% is made up of vascular dementia caused by multiple strokes, alcoholism, Parkinson's disease, and drug intoxication. The term Alzheimer's disease originally meant presenile or early onset dementia but it is now used to describe any progressive dementia with the characteristic pathological changes.

AD (Alzheimer's disease) is characterized by a progressive process that kills brain cells and destroys synaptic connections between nerve cells in the brain. The disease is traditionally characterized by the presence of what are called "neuritic" or "senile" plaques, neurofibrillary tangles, and the loss of nerve cells that rely on acetylcholine as a neurotransmitter as explained below.

The core of the "neuritic plaques" is composed of beta-amyloid protein (AP), which is a minor breakdown component of amyloid precursor protein (APP). This APP normally gets broken down into fragments in the brain, and one of the fragments can be AP. Excess AP gets deposited and causes the development of the neuritic plaques. The phenomenon of APP in the brain not being handled properly and causing AP to form neuritic plaques is considered to be a primary or at least a very significant cause of dementia.

Neurofibrillary tangles (tau) look like tangled hair. They consist of spirals (paired helical filaments) of abnormal protein (an important architectural component of nerve cells). Tau is like the framework of a house -- the house being the nerve cell. It does not normally tangle, but when the brain cells inexplicably add phosphate groups to it, it spirals and tangles.

Neuritic plaques and tau impair the healthy functioning of nerve cells causing some to die. The most sensitive ones die first. These are usually the cells that secrete acetylcholine as a neurotransmitter for communicating with other cells.

The sequence of changes that occur in the brain with AD can be divided into four basic categories:

• Primary events relate to genetic factors and some spontaneous nerve-cell deaths, or apoptosis. Generally, nerve cells do not and should not die.

• Secondary events cause synaptic loss, or loss of nerve interconnections. These include the beta-amyloid problem and cell-architecture (cytoskeletal) and tau changes, especially of the cholinergic neurons (nerves using acetylcholine as a neurotransmitter).

• Tertiary events occur when brain cells start dying. They release amino acids like glutamine which can cause a damaging reaction due to overexcitation of nerve cells which in turn causes neurotransmitter problems, atrophy and immune dysfunction.

• Quarternary events occur when the death of brain cells also causes inadequate circulation and nutrition in the brain.

The prevalence of AD goes up rapidly with age. If you live long enough, your chance for developing AD could be more than 50% (see below). Since people today are living longer, AD is increasing rapidly. The number of deaths from AD in 1993 were 20 times those in 1979.

60 to 65 years      0.4% to 1%

85 to 90 years      20% to 40%

95 years              55%

The nerve-cell loss that occurs with the onset of AD might start at around age 40, but by the time the person shows symptoms at age 60 to 70, a large percentage of the damage has already been done. That means that prevention is your best weapon in the fight against this disease.

There are a number of other possible risk factors associated with Alzheimer's disease. The most common and generally acknowledged are family history, genetics, sex (risk is higher in females), Down's syndrome and aluminum. Late onset AD is probably more a lifestyle / environmental disease, perhaps with some genetic tendencies, as opposed to early onset AD, which definitely has a high genetic association.

Alzheimer's disease is expected to cost the United States $100 billion in nursing, research, treatments and Medicare expenses, etc. by the year 2010.

For information on natural treatments for Alzheimer's Disease, see Flower Power for Alzheimer's Sufferers and look up Alzheimer's in  the Story Links section of the Links page on this site.

Also see: Aluminum and Alzheimer's.

Also see: Water: The Misunderstood Nutrient