Alzheimer's: Nature or Nurture?

We know that both our genetics and our lifestyle contribute to the development and advance of Alzheimer's disease.  But which is more powerful?  A good question, and new research just published in the journal Brain shows some clues.  At least it shows some clues on how the question may be further pursued.

The research was led by Anouk den Braber and Pieter Jelle Visser at VU Amsterdam.  It studied 39 pairs of identical twins in their 60s and 70s and evaluated their load of abnormal tau protein.  Some also showed the presence of beta amyloid, while others did not.  (Abnormal tau and beta amyloid are markers for Alzheimer's disease.)  Identical twins, of course, have identical genetic makeup, and there was a strong correlation between the appearance and distribution of the tau and the presence of amyloid markers among the twins, but it wasn't complete.  In 86% of cases, researchers could identify twins simply by examining the distribution of tau in their respective brains.

The twins voluntarily submitted to a variety of fMRIs and PET scans the researchers used to identify the amyloid and tau distribution.

The researchers were particularly interested in how lifestyle differences might affect the markers, especially tau.  They were particularly interested in exercise habits, obesity, and social activity.  This is a bit challenging, because, as we noted in Beating the Dementia Monster, family members usually share lifestyle choices, both good and bad.

But a few of the twins did not share all of the lifestyle features of their siblings, and there was some indication that these correlated with differences in Alzheimer's disease markers.  Some twins showed the presence of amyloid plaques, when their siblings did not.  Unfortunately, there were not enough examples of differing lifestyles to be statistically significant.  This was partly due to dropouts from the study.  I'm guessing that covid didn't help that situation. 

In the end they concluded that this was a good way to explore the relative influence of genetics and lifestyle on the development of Alzheimer's disease.  But someone needs to try again with a bigger, more robust cohort of subjects.

More reading on this here.