Cognitive ability looks to be fairly fixed throughout adulthood

A longitudinal study of 1000 men has found that general cognitive ability (GCA) at age 20 is a stronger predictor of how it will be later in life than education, occupation or other activities. 

“The findings suggest that the impact of education, occupational complexity and engagement in cognitive activities on later life cognitive function likely reflects reverse causation,” says first author William Kremen, from the University of California San Diego in the US, adding that “they are largely downstream effects of young adult intellectual capacity”.

In other words, high-level cognition leads people to engage in complex mental tasks, rather than the tasks shaping the brain. 

The findings are reported in a paper published in the journal PNAS.

Kremen and his team report that GCA at age 20 accounted for 40% of the variance in the results taken at age 62.{%recommended 8403%} 

Further, they found that GCA at age 20 is correlated with surface area of the cerebral cortex at age 62. The cerebral cortex is responsible for cognitive function, such as thinking and using language. No correlation was found for education. 

The participants were all part of the Vietnam Era Twin Study of Aging and were tested with the US Armed Forces Qualification Test. 

While the results suggest GCA is relatively fixed across adulthood, the researchers point out that this could mean education in early life is even more important than previously thought. 

“Strengthening cognitive reserve and reducing later-life cognitive decline and dementia risk may really begin with improving educational quality and access in childhood and adolescence,” they write. 

Doctors often recommend that older people do crossword puzzles or engage in other brain-stimulating activity to keep their mental acuity sharp, but that approach might be too little, too late.

“Our findings suggest we should look at this from a lifespan perspective,” Kremen says. “Enhancing cognitive reserve and reducing later life cognitive decline may really need to begin with more access to quality childhood and adolescent education.” 

Still, maintaining cognitive function later in life remains a complicated issue. While the researchers found little affect from occupation and education, some 60% of variance in the GCA scores remains unaccounted for. 

A separate study recently found that frailty in old age is linked to dementia and can negatively affect treatment options. 

Another study found that single people have a much higher risk of dementia than married people. 

So while being a smart youngster might bode well for later cognitive function, long-term brain health is hardly a fait accompli at age 20.