THE BLOG
08/13/2013 05:21 pm ET | Updated Oct 13, 2013

An Introduction to Genetics and Alzheimer's Disease

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With a lack of treatment or cure for Alzheimer's, many are concerned about the prospect of developing a disease which places an enormous financial, emotional, and physical burden on families. According to a survey conducted by the MetLife Foundation, Alzheimer's disease is the second most feared disease -- behind only cancer. Three in 10 Americans identify Alzheimer's as the disease they are most afraid of getting.

As baby boomers head into their golden years, the senior population, those 65 and older, is predicted to double in the next 20 years. Currently, age is the greatest known risk factor for Alzheimer's. However, family history also plays a role and should be taken into consideration as many look for answers about their risk for the disease.

Genetics is one of several variables involved in the development of Alzheimer's. Individuals with a first-degree relative like a parent or sibling with Alzheimer's have a 10 to 30 percent increased risk of developing the disease.

The apolipoprotein E (APOE) is a gene that helps determine one's risk of developing of both early-onset and late-onset Alzheimer's. However, the APOE gene is different than genetic mutations that cause the more rare autosomal dominant Alzheimer's, which is thought to account for less than 1 percent of all Alzheimer's cases. APOE has three common versions:

• e2 is a relatively rare form of the gene and may provide some protection against the disease.
• e3 is the most common form and is thought to neither decrease nor increase the risk for the development of Alzheimer's.
• e4 occurs in 25 to 30 percent of the population and approximately 40 percent of all people with late-onset Alzheimer's have this version. This form of APOE increases the risk of developing Alzheimer's; however, the reasons for this are still being determined.

It is important to note that everyone has two APOE genes, but each gene can have a different version (e2, e3, or e4). The risk of developing Alzheimer's and at what age an individual starts to develop symptoms is tied to the number of copies a person has of the e4 version. For example, a person's risk of Alzheimer's may be as high as 90 percent if each copy of APOE is the e4 version (with an average age of onset of 68 years), whereas having no copies of e4 puts the risk of developing Alzheimer's at 20 percent or less (average age of onset being 84 years).

Although APOE e4 increases the risk of developing Alzheimer's, it does not mean for certain you will develop Alzheimer's. Some people with one or two copies of e4 never get the disease, and many others who develop Alzheimer's do not have any copies of the e4 version.

The possibility of developing Alzheimer's haunts much of our aging population. However, the Alzheimer's Prevention Initiative is pushing research forward to find a breakthrough that will ultimately stop or slow the progression of the disease. Led by the Banner Alzheimer's Institute, one groundbreaking study -- which investigates whether an anti‐amyloid treatment can stave off the disease -- will span two countries and help launch a new era of prevention research in the urgent fight against Alzheimer's. And this movement is only getting started, with future prevention research and trials expected to launch within the next year.

You can help us move prevention research forward by joining the Alzheimer's Prevention Registry. The Registry plays matchmaker, connecting healthy individuals with scientists conducting Alzheimer's prevention research in their own community. Visit www.endALZnow.org to learn more and to join the Registry. Every person who signs on brings us one step closer to stopping this disease. The memories you save could be your own.