More on exercise and brain volume

In Beating the Dementia Monster, we cited research finding that even moderate exercise could increase brain volume.  In one study, researchers found that just working in the garden for a year could produce a measurable increase in brain volume.  My neurologist warned, however, that there is not an established correlation between an increase in brain volume and improved memory & cognition.  I've read several studies regarding increased brain volume, and none of them seemed to look for or find a corresponding change in memory & cognition.

And so, speaking of studies on changes in brain volume, there is a brand new one.  It was "Association Between Accelerometer-Derived Physical Activity Measurements and Brain Structure," published in the September issue of Neurology, the journal of the American Academy of Neurology.  What was new in the study was that it found a remarkable increase in brain volume when someone begins exercising a small amount during the week, but there are diminishing returns when the amount of exercise per week is increased.  (Also novel, they used an instrument called an accelerometer to measure how much exercise each test subject was actually getting.)

The study did not appear to look for a concurrent improvement in memory and cognition, even though it mentions neurodegenerative diseases, like Alzheimer's disease.

These results are not consistent with my experience.  I've had seven MRIs of my brain since my initial diagnosis in 2015, and they showed a steady trend of continuing atrophy.  At the same time, my memory and cognition appeared to improve, at least through 2019.  (My neurology care team says it has been stable since 2019, although they found some improvement in 2021.)

You will recall from Beating the Dementia Monster that I joined the gym in December 2015.   This followed decades of a sedentary lifestyle.

When the radiologists look at an MRI, they measure the volumes of the hippocampus and the ventricles (these have been trending toward atrophy), but they also norm them with respect to other men my age.  So while the volumes have been going the wrong way in absolute terms, the normed value of my hippocampus volume has gone from < 1 percentile in 2017 to the 56 percentile in 2020.  That's comforting, but may represent differences in equipment and technique.

So what do we make of the correlation between exercise and memory & cognition?  I still stand by the research we discussed in chapter 8 of Beating the Dementia Monster.  In people who have developed or are known to be developing Alzheimer's disease, memory & cognition begin to improve with an hour or two per week of exercise.  This plateaus at about five and a half hours per week, but memory & cognition begin to decline after about eight hours per week.  In the healthy control group, exercise did not influence memory & cognition.   Consistent with my experience, at about 5 and a half hours per week, memory & cognition were nearly the same as the control group with age-related normal memory loss.