Wednesday, May 25, 2011

Population prevalence of the ApoE4 gene

Regarding the Alzheimer genotype, I just did a little research regarding the prevalence of the ApoE epsilon 4 allele (the allele that predisposes to Alzheimer disease). Depending on the study you read, about 20% of the population has at least one epsilon 4 allele, while about 2% have two epsilon 4 alleles. As you'd expect, having two is worse than having one in terms of Alzheimer risk. I should add that the epsilon 4 allele also predisposes to a worse outcome in recovery from traumatic brain injury and is also over-represented among those football players who suffer from Chronic Traumatic Encephalopathy.

It's important to note that this data applies only to those of European ancestry. The rates of other ethnic groups are different. I saw one study showing, for example, that the rate of epsilon 4 prevalence is much, much higher among Australian aboriginal populations.
I recently sent in a saliva specimen to to have their CLIA-approved lab run a genetic profile on me, which will include a report on my ApoE status. The service has dramatically decreased in price in recent years, so I finally broke down made the purchase. I'll report those results when I get them next month.


Forensic Pathology Blog said...

I can't wait to see your results. having suffered from several sports-related concussions, maybe I should get mine done. But then again, not really sure if I want to know!

jd said...

Why would you do that? If you come back 4/4 or 3/4, that'll be hanging over you the rest of your life. If there were a cure for Alzheimer's, that'd be different.

Brian E. Moore, MD said...

To jd:
ApoE status doesn't just inform an individual about risk for Alzheimer's, but also gives an indication about recovery from head trauma, and perhaps about the risk of developing chronic traumatic encephalopathy. Regardless of that, though, knowledge in itself has intrinsic value, regardless of whether or not I can do anything about treating Alzheimer's in the event that I develop it.

Jamie said...

Choosing to know ones ApoE4 genotype is something that should not be taken lightly. I inadvertantly discovered mine when participating in a study. There was no genetic counseling involved and my knowledge about what this information actually meant was not given to me during the informed consent process. I have just been diagnosed with PTSD because of this information and the lack of preperation and knowledge regarding the testing. I definately was "shell shocked" by the results.

I have 2 copies of the ApoE4 allele which puts me at a 91% risk of getting AD per previous studies with Duke.

Depending on the company that does the testing, the results will very and there is much ambiguity at best with these companies as to what the risks really are and mean. That is why the FDA is now attempting to regulation the direct to comsumer marketing with genetic risk testing companies.

The consumer needs to be aware that there is no evidenced based studies that support prevention or cure. Healthy denial can be a good thing, and knowing ones AD risk my not be helpful (especially if one has experienced a loved one having passed with this horrible disease). In addition, one is at a huge risk if you do not already have "long term care" insurance.

Experiening the symptoms of PTSD has not been easy. There are not any support groups that I am aware of for those of us who know our genotype and this has been quite a lonely journey. I hope you chose to post my comments. I am not saying not to test, but consumers need to be aware of just what the ramifications mean, lifetime risk of disease, average age of onset for specific genotype, possible discrimination, and lack of ability to get "long term" care insurance.

The only reason I could suggest or advocate this testing is if it motivates one to participate in research.


TulsaEyeGuy said...

A silver lining is the ApoE4 gene imparts great protection against the number one cause of permanent blindness in the western world- macular degeneration. Zareparsi et al, May 2004 and Edward Loane et al, May 2011