Possible Causes Of Alzheimer’s Disease

September 10, 2007

The cause for Alzheimer’s disease is unknown. The ultimate solution for the many problems that result from this disorder is to find the cause and to prevent the disease. At present several intriguing possibilities exist.

The Unconventional Virus Hypothesis

The strongest evidence linking Alzheimer’s disease to an unconventional “slow” virus infection results from the discovery that other rare neurological diseases previously thought to be degenerative in nature have now been shown to be caused by transmissible virus like agents. The rare neurological diseases that now fall into this category consist of Kuru, Scrapie (a disease of sheep), and Creutzfeldt Jakob disease. Kuru and Creutzfeldt-Jakob disease both eause dementia in humans. Transmission experiments have been carried out which consist of taking a Kuru, Scrapie, or Creutzfeldt-Jakob brain and injecting the filtered tissue into the brains of animals. These experiments have demonstrated, after a latency of many years, that the neurological disease could be transmitted to the animal.

Substantial effort has been expended in an attempt to transmit Alzheimer’s disease to nonhuman primates, such as chimpanzees, but without success. Some investigators believe that failure to transmit the disease may result from an unsuitable host; they do not believe that the inability to transmit precludes the possibility that Alzheimer’s disease is caused by an unconventional viruslike agent.

What does seem clear is that persons exposed to Alzheimer victims do not have an increased chance of developing the disease. Although special procedures are necessary for handling the blood and cerebrospinal fluid of patients with Creutzfeldt-Jakob disease, no such precautions are deemed necessary for Alzheimer’s disease.

The Genetic Hypothesis

Alzheimer’s disease is not a strongly genetic disorder such as diabetes mellitus or Huntington’s disease, nevertheless a slight genetic risk for Alzheimer’s disease results from the presence of a family member with the disease. The risk for the family member of an Alzheimer victim may be strongly influenced by the age of onset of the disease. For example, Alzheimer’s disease that has its onset at age forty may present a 40 percent risk for family members. In contrast, Alzheimer’s disease beginning after the age of eighty brings about little or no increase for the family member as compared to the general population.

Family members of Alzheimer victims frequently ask whether they are at increased risk for developing the disease. Unfortunately, at present no good predictor exists as to who will develop the disease. In addition, the typical late onset of Alzheimer’s disease makes it impossible to carry out effective family planning. At present the best advice that can be offered is a rough estimate of risk based on the age of onset of Alzheimer’s disease in the affected family member.

The Aluminum Hypothesis

Scientific claims have been made that the brains of Alzheimer victims contain increased amounts of aluminum. Also the feeding of large amounts of aluminum to laboratory animals has been shown to bring about neurofibrillary tangles, which is one of the characteristic microscopic features of Alzheimer’s disease. These reports have in the past received substantial coverage in the popular press and have given rise to great concern regarding the usage of aluminum cookware, drinking water in which aluminum was used in the purification process, or even breathing air containing substantial amounts of aluminum.

The aluminum hypothesis has been seriously questioned. The neurofibrillary tangles associated with aluminum, when examined under the electron microscope, appear different from those seen in Alzheimer’s disease. In addition, other scientists have not been able to replicate the findings of increased amounts of aluminum in the brains of Alzheimer victims. A general loss of enthusiasm for the aluminum hypothesis has thus occurred in recent years, although the role of aluminum or other environ mental agents as a cause or facilitator of the disease does remain a possibility.

Posted in Alzhemier Disease