There is a mountain of evidence supporting the connection between rigorous mental activity through the lifetime and reduced rates of cognitive decline in older age. However, despite the repeated demonstrations of correlation between these two factors, whether or not one causes the other has yet to be determined.

It is possible that people who seek out challenging mental tasks, careers, and higher education throughout their lives may do so because of a genetic predisposition that serves to protect them from dementia.

Developing an understanding of exactly how cognitive activity and decline interact with each other is important, especially given the companies who seek to profit off of the notion that it is the challenging mental activity that prevents the decline. Common assumption tends to lean toward this being the accepted public knowledge, but testing on the products developed to capitalize on this assumption are inconclusive at best.

Research does seem to indicate, though not conclusively, that there is a protective factor in challenging mental activity. A new study published in JAMA Neurology this week found that people with lifelong histories of mentally challenging careers and higher education were able to perform better in cognitive testing. The same was true for those whose histories involved education or career choices taken on later in life.

When taking genetics into account, the same effect could still be found. The study estimated that elderly participants carrying the APOE4 gene, recognized as a significant indicator of the age of onset for cognitive decline, would experience dementia or other types of decline later if they were highly educated and challenged in their careers. More specifically, those in the 75th percentile would be estimated to experience a delay in decline of about 8.7 years later than peers located in the 25th percentile.

The study does not do enough to prove causality. As people are allowed to make their own educational and career choices, the amount of controls necessary to establish cause and effect prevent the ability to prove causality. The shoddy quality of the studies conducted on “brain training” products also does little to establish a causal link.

More than just consumer products would benefit from the continued pursuit of the causal link between cognitive activity and preservation. Approaches to medical care throughout the lifetime, but especially in elderly populations, would be better developed if this missing piece of information was found.