Alzheimer's Disease Causes & Risk Factors

Conditions & Diseases: Brain & Nervous System

Alzheimer's Disease

Causes & Risk Factors

The exact causes behind Alzheimer's Disease are yet to be identified, however, age is considered as one of the most important factors with risk of the disease doubling every 5 years beyond the age of 65 (9).

Most cases of Alzheimer’s disease are due to a “...variety of factors acting together,” with the exception of familial Alzheimer’s disease (FAD), wherein mutations on a single gene is considered the principal cause.

However, research studies on FAD have revealed that proteins namely amyloid precursor protein (APP) and two presenilins are causal agents for both FAD and Sporadic Alzheimer’s disease.

“Mutations in the genes that encode APPs and the presenilins can cause Alzheimer’s disease.” (9)

It is important to note that “...changes in other genes may not cause Alzheimer’ disease,” but certainly tend to increase the risk to develop Alzheimer’s disease. The well-known risk gene and its alleles that encode apolipoprotein E (apoE) can increase the risk of Alzheimer’s disease.

The apoE gene exists in three allelic forms namely apoE2, apoE3 and apoE4. While apoE3 occurs most commonly in the general population, apoE4 occurs in about 40% of late onset AD patients. An offspring who inherits one each apoE4 allele from each of the parents is highly susceptible to be affected by AD as compared apoE3. Similarly, an offspring inheriting apoE2 is least likely to develop AD.

Acetylcholine, serotonin, somatostatin, and noradrenalin reach below normal levels in people suffering from AD. Acetylcholine is an important neurotransmitter and found in abundance in the nerve cells of hippocampus and cerebral cortex i.e., the regions affected by Alzheimer’s disease.

In addition, studies also show that people who suffer traumatic head injuries and women are more at risk of suffering from the disease (2). High blood pressure and cholesterol and poorly controlled diabetes are also some of the contributing risk factors to Alzheimer's Disease (10).

Article by Kona Vishnu, MS
Medical Writer,
OmniMedicalSearch.com