A study published this week in JAMA Neurology adds to the already large body of evidence indicating that people who engage in vigorous mental activity throughout their lives tend to slide more slowly into cognitive impairment than those whose brains sit on the couch eating bonbons.
But it remains uncertain whether “lifetime intellectual enrichment,” as the study authors called it, is cogno-protective in and of itself, as opposed to a surrogate marker for some other protective factor.
The issue is important because clever entrepreneurs are increasingly hawking “brain training” products, billed as helping to prevent age-related cognitive decline, to the worried middle-aged well. Lumosity is the best known but there are many others. The evidence base that these games and mental exercises actually do long-term good is thin at best.
In the new study — one of a series examining residents of Olmsted County, Minnesota, home of the Mayo Clinic — 277 people who had developed mild cognitive impairment were prospectively compared over 5 years with 1,718 others who scored cognitively normal.
Participants, who were in their mid-70s to early 80s, were quizzed at baseline about their job types and 10 categories of cognitive activity in which they engaged in the previous year and when they were 50 to 65 years old. Their performance on cognitive tests was tracked from enrollment through the follow-up period.
Not surprisingly, those with higher educational attainment and more mentally challenging employment at baseline had higher cognitive performance throughout the study period; moreover, even within categories of education/occupation level, those with higher middle- and late-life levels of cognitive activity also performed better.
APOE genotype was also a significant factor in predicting age at onset of cognitive impairment, but “intellectual enrichment” appeared to be protective in this group too. The study authors, led by Mayo’s Clifford Jack Jr., MD, estimated that an 80-year-old APOE4carrier at the 75th percentile of education, occupation, and mid/late-life cognitive activity would develop cognitive impairment 8.7 years later than one at the 25th percentile.
Jack and colleagues called the association a “protective effect of intellectual enrichment,” repeating the word “effect” throughout their discussion. But was it really an effect, a word that implies causality?
It certainly could be, and no one would argue that individuals shouldn’t be encouraged to be as active mentally (as well as physically) as possible throughout life.
But this wasn’t a randomized trial. The Olmsted County residents long ago chose (or had chosen for them — the distinction doesn’t matter in this context) what jobs they would hold, how long they would stay in school, and what types of mental activity they would undertake later on.
Neither the Mayo team nor anyone else has yet ruled out the possibility that people who make the choice to go to college, to go into professional-type careers, and to work crossword puzzles are already resistant to cognitive impairment, because of genetics or some other factor already in place in adolescence if not before.
And the benefits of “brain training” for delaying or slowing cognitive decline are still mostly theoretical. The studies touted by Lumosity as backing its program for older healthy adults have all been either uncontrolled or very small, and none of the controlled studies tracked participants for more than a few months.
Some interventions have shown clear benefits while participants were actively pursuing them, but again, follow-up in those trials was either short or nonexistent.
Importantly, a recent study that did examine long-term outcomes in people who had undertaken a mental-exercise intervention found no benefit in their ability to perform activities of daily living.
So, by all means, keep going in your professional job and take up crosswords or Sudoku if you like. Just be open to the possibility that wanting to do those things — not the actual doing of them — is the cogno-protective factor we all seek.
Striking a Nerve is a blog by John Gever for readers interested in neurology and psychiatry.