Alzheimer's and Genetics

Alzheimer's is a disease that has affected the lives of many elderly people who were once fit, active, and social. It can be a heartbreaking experience to see loved one’s loosing memory, social competence and more, and would be a tremendous disease to find a cure for. Research on the genetics of individuals and how that may relate to those who are diagnosed with Alzheimer’s may be a great step in the right direction.

         First of all, it is essential to understand that there are two different types of Alzheimer’s: familial AD and sporadic AD. Familial AD is not as common, as it accounts for not even 10% of cases. Symptoms of this become present much younger, between the ages of 30 and 65. Only one copy of this mutation on chromosome 1, 14, or 21 is needed to develop the disease. While these discoveries have certainly aided in the research of familial AD, it only accounts for 50% of all familial AD cases, leaving the other 50% to an unknown gene or genes that are affecting this.

         On the other hand, sporadic AD is much more prevalent today, affecting approximately 90% of Alzheimer’s patients. The onset of this form of the disease is typically not seen till after the age of 65. While this is certainly the more common disease, researchers are also having a harder time linking it to any specific pattern of inheritance. They have, however, discovered the APOE gene on chromosome 19 that is believed to have an “associated risk” to sporadic AD. The different alleles (forms) of this gene are e2, e3, and e4. Researchers believe that those with the e4 allele, especially those who inherit an e4 allele from both parents, are more likely to have sporadic AD, but unlike familial AD not everyone with this allele will develop the disease.

         Sporadic AD is the without a doubt the more common form of Alzheimer’s seen today, therefore leading me to further research on just how much the APOE gene affects individuals, and if this shows promise of future discoveries and potential cures. According to studies in the Journal of Neurology, Neurosurgery & Psychiatry the APOE genotype affects those of varying ages and sexes differently. As seen in the previous research the e4 allele corresponds with many Alzheimer’s patients; however, this study also shows that the gene has a stronger effect in men than women. In addition to this, the e2 allele appears to aid in the prevention of this disease, but only in “younger-old people.”

         After comparing numerous sources it all seems to conclude the same points, the first point being that the e2 allele appears to reduce the risk of Alzheimer’s, the e3 allele has little or no affect, and the e4 allele increases the risk of having this disease. While this information is certainly steps to curing this disease, it is certainly not the end. All the research seems to conclude that although an allele may increase the risk of AD it is not in itself what causes it. There have been cases of people without the e4 allele who suffer from Alzheimer’s as well as those with it.

         While there is no definite cause or cure, I don’t think it is out of the question that we will see one in our lifetime. As our knowledge of genetics increases I hope to see ways that we can treat and prevent a disease that has become far too common and affected so many people today.



Sources:
http://www.ygyh.org/alz/whatisit.htm
http://jnnp.bmj.com/content/75/6/828.short
http://www.mayoclinic.org/diseases-conditions/alzheimers-disease/in-depth/alzheimers-genes/art-20046552