Does Size Matter?

Posted on March 31, 2011


Fortunately, at least when it comes to dementia and certain brain injuries, the answer is no.  That’s thanks to something referred to as one’s “cognitive reserve.”

cognitive reserve

Marked hydrocephalus, compared with a normal brain CT on the right.

When comparing the two images, you might assume that the owner of the brain on the left has severely reduced mental capacity – but you’d be wrong.  That decimated flap of gray matter belongs to a French tax official (I’ll refrain from jokes) who “lives a completely normal life.”  This is an extreme case of resistance to cognitive impairment, but wonderfully illustrates the fact that we can lose significant amounts of brain tissue to pathology and retain function.

What is cognitive reserve?

Cognitive reserve is a somewhat nebulous term used to describe the brain’s ability to compensate for neurological injury or degeneration and preserve function.  It is perhaps best thought of as a buffer for one’s mental capacity.  Individuals who have greater cognitive reserve are able to, in a sense, “mask” neurological degeneration, and even stave off the onset of certain diseases by years.

Take, for example, Alzheimer’s Dementia (AD):  it begins with impairment of learning and memory, then progresses to speech and comprehension difficulties, and eventually orientation to time and place.  The idea of cognitive reserve was borne of intriguing observations made in the context of dementia, especially Alzheimer’s.  One study concluded that 25-67% of those diagnosed with AD post-mortem had no clinical manifestations of the disease in life (Scarmeas et al., 2004). 

Researchers don’t actually understand the process behind cognitive reserve completely, but trends and correlations exist, and that’s what I’d like to share with you.

How can I maximize my cognitive reserve?

Unfortunately, some factors are out of our control – be they genetic, environmental, or even part of our childhood development (in other words, the train has already left the station for some factors).  Other factors like exercise, your social network, education, and even leisure activities – all of which have been studied in relation to cognitive reserve – are within your power to control.

One cohort study showed that the risk for developing dementia was 2.2x higher for those with <8 years education (Stern et al., 1994). Another concluded that individuals who engage in intellectual or social leisure activities have 38% less risk of developing dementia (Scarmeas et al., 2001).  Most interestingly, for individuals of the same education and occupation, those with higher physical demands were able to better tolerate brain pathology.

Older individuals can also take measures to improve cognitive reserve – here’s a partial list of activities that may delay the onset of clinically apparent mental decline:

  • Exercise (make it load-bearing and you’re fighting osteoporosis, too; future post)
  • Traveling
  • Gardening
  • Knitting
  • Reading newspapers, magazines, and/or books
  • Playing cards, games (yes, including bingo!)
  • Visiting or being visited by friends or relatives (don’t forget how important this is)
  • Playing musical instruments
  • Dancing
  • Participating in community activities
  • Developing an extensive social network
  • Having close friends/confidants

So consider taking action that may help you live a longer, fuller life.  Pass this information along to an elderly loved one – in fact, you can kill two birds with one stone by teaching them to use email (if they don’t already know how – which, if you’re not getting tons of chain letters from them, they probably don’t)!

“Being on a sitcom stops me from getting Alzheimer’s.”

-Jerry Stiller



Posted in: Health, Medicine