Monday, March 10, 2008

60 is the trigger for Alzheimers

Finally, a weekday post! I know, I have gotten in this vicious cycle of posting on the weekends and keeping them up for the first few days of the week, just so those readers who don't check the rss or even switch on a CPU on the weekends don't miss a beat. Listen, I read Tim Ferriss' book too...but I now have to step it up.....

Today I want to bring an interesting topic to light. Why are people scared of genetic testing? Is it the discrimination (which doesn't exist) or is it something more deeply rooted like "Genetic Determinism"? In counseling for things like breast cancer risk, some often say..."You may have outlived your risk for early onset breast cancer" This is a sticking point for me.....Who ever outlives genetic risk? Completely, I mean. There are so many variables out there that can give you cancer...who is to say that just because you are 65 your BRCA mutation won't give you that cancer? I couldn't be hard pressed to say that so vociferously. I say this because even with the strongest genetic influences there is always an exception. This is exactly the case with Alzheimers and ApoE4.

Well now a study recently released called the Arizona ApoE4 Cohort Longitudinal Study of Cognitively Normal Individuals (Say that 3 times fast) indicates that 60 may be the age of kickoff for cognitive decline in ApoE4 carriers.

According to the article in Internal Medicine News......
There is a particular pattern of decline in ApoE4 homozygotes (2 copies) that tend to precede any diagnosis of mild cognitive impairment (a stage prior to full blown alzheimers or other dementia). Or prior to anything that can be seen on radiologic brain imaging....

So what does this mean for the clinician? It is huge....Instead of outliving your risk...we now may identify those with ApoE4 who will likely get Alzheimers......CAUTION, these results are currently being replicated and I wouldn't want to promise anyone that we have a perfect ApoE4 phenotype detector quite yet. But it is important to have this....Why? Because up to 10-40% of homozygotes will NEVER develop Alzheimers. So when can we say you have "Outlived your risk"? The answer is never...but we can say "You will be less likely to have ApoE4 related Alzheimers than someone who is your same age with this cognitive deficit." That is what should be said.

Now the real quandary..."How can we stop it from getting worse doc?" That is for another post.

The Sherpa Says:
Too many in the genetics field are quick to give medical advice. I warn that perhaps we should check our training and liability insurance before we start doing this. I recommend that all of us in this field work together to provide the best care possible. I never say never and never say genetics as in life, there are NEVER any definitive answers...except "sometimes" and "it depends" That being said..........We should always be performing routine screening exams on carriers of any genetic changes. Confused yet? Don't be. Just follow my lead.

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