EXERCISE: THE DEMENTIA SLAYER?
One gene in particular, the ApoE4 allele, continues to come
up throughout this book. While far from a sentence to
develop dementia, it is the only well-defined Alzheimer’s
risk gene, and having one or two copies does increase the
likelihood that a person will develop cognitive decline.
Research suggests that exercise can negate some of the
gene’s observed influences on the brain. It does so in part
by “normalizing” brain glucose metabolism, which is
reduced in ApoE4 carriers (discussed in chapter 6), and
reducing plaque buildup, which seems to be accelerated in
carriers. Interestingly, the ApoE4 allele is considered the
“ancestral” (i.e., oldest) variant of the ApoE gene, having
emerged at a time when we had to chase our food. Its
negative association with modern disease may be merely a
consequence of our recent transition to relative inactivity,
amplified by our industrially mangled diets.
If neurological decline is one consequence of inactivity,
might becoming more active actually reverse cognitive
impairment? Researchers sought to answer this question in a
2013 study, ultimately finding that sedentary people with
mild cognitive impairment (MCI) improved their memory
and the efficiency of their brain cells after just three months
of regular exercise.^7 The study also included a group of
cognitively normal people who saw similar benefits. What’s
more, the subjects improved their cardiorespiratory fitness
by just 10 percent, suggesting big cognitive gains for a
relatively small boost in fitness.