Exercise vs Dementia in APOE4 Positive Adults

I thought I'd finish this week by looking at bit more at fitness.  One of the bigger questions today for family members caring for loved ones felled by Alzheimer's disease (or any other dementing illness, for that matter) is whether or not they're going to be diagnosed with said illness.  In other words, what's their risk?  And especially because a family member is involved, is there any way to check for genetic predisposition?

Most of us have heard about the APOE4 allele and its link to Alzheimer's disease.  However, we still don't recommend checking it in everyone because it's neither sensitive enough nor specific enough.  In other words, just because you turn up positive doesn't mean you'll eventually be diagnosed w/Alzheimer's disease.  Likewise, just because you turn up negative doesn't mean you won't eventually be diagnosed.  So what's the use?  Well, clearly those who are positive are at greater risk than those who are negative.  

But in a study published earlier this month in Archives of Neurology, the authors assessed 201 cognitively normal adults avg age mid-late 60s, over half of whom were female for both APOE status and presence of amyloid in cerebral spinal fluid (CSF) and on contrast imaging.  They then correlated these findings to lifestyle, specifically physical activity.

It turns out that those cognitively normal patients who were APOE4 positive had more amyloid in their brain (based upon imaging with Pittsburgh Compound B) and not as much in their CSF compared to APOE4 negative participants.  More importantly, those who were APOE4 positive AND sedentary had even more amyloid deposition compared to APOE4 negative participants, after taking into account the usual suspects, eg age, sex, education, body mass index, blood pressure, diabetes, heart disease, and depression.

In other words, if you are APOE4 positive and thus at greater risk for Alzheimer's disease, you might be able to mitigate your risk by exercising which is associated with less amyloid deposition.  This hypothesis certainly supports the current trend in research regarding the general health and disease-specific benefits of regular exercise.  As I noted in my presentation earlier this week at our state's winter meeting, it's never too late to start exercising!

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