Some Aspects Of Cognitive Ability Start to Decline In Late 20s

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Main Category: Neurology / Neuroscience
Also Included In: Mental Health;  Seniors / Aging;  Psychology / Psychiatry
Article Date: 18 Mar 2009 - 9:00 PDT

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New research from the US suggests that some aspects of cognitive or mental performance such as speed of thought, reasoning and spatial visualization peak at age 22 and start to decline at around age 27.

The study was the work of Professor Timothy Salthouse of the University of Virginia and is published in the April issue of the journal Neurobiology of Aging.

Salthouse wrote that cross-sectional studies have consistently shown that increased age is linked to lower levels of mental or cognitive performance, even in those aged between 18 and 60.

However, he explained that many people question the validity of using cross-sectional studies to investigate age related qualities because they compare differently aged people and don't compare people against themselves as they get older, as for example longitudinal studies that retest people as they get older might do.

But this can also give problems because if you keep retesting the same people, it is difficult to separate out any effects that might arise from them knowing what to expect in the tests and getting better at doing them each time. Such effects could mask any results from longtudinal studies that might show a lower propensity for cognitive decline with age, which is what Salthouse found:

"The results of the current project suggest that a major factor contributing to the discrepancy is the masking of age-related declines in longitudinal comparisons by large positive effects associated with prior test experience," he concluded.

Salthouse said that when he put together the results from three ways of estimating the effects of retesting people, with findings from other studies that compared animals raised in constant environments, and studies that looked at neurobiological variables that are not susceptible to the retesting effect, he concluded that:

"Some aspects of age-related cognitive decline begin in healthy educated adults when they are in their 20s and 30s."

Salthhouse studied 2,000 healthy 18 to 60 year olds for 7 years and found that some aspects of cognitive ability peak at around age 22 and start to decline at around age 27. These were speed of thought, reasoning and spatial visualization or ability to visualize and solve problems.

He used the same tests that doctors use in dementia screening to test the participants' ability to solve puzzles, recall words and details of stories, as well as notice patterns in letter and symbols, according to a BBC News report.

The results showed that in 9 out of 12 tests, the top performance was at age 22, and after age 27, tests of brain speed, reasoning and ability to solve visual puzzles, showed consistently poorer results.

However, other areas of mental ability did not decline so early, reported the BBC. Salthouse found that memory stayed the same until around age 37, and other things like abilities that rely on accumulated knowledge kept increasing until the age of 60.

"When does age-related cognitive decline begin?"
Timothy A. Salthouse
Neurobiology of Aging, Volume 30, Issue 4, April 2009, Pages 507-514.
doi:10.1016/j.neurobiolaging.2008.09.023

Click here for article (via DOI link).

Sources: Journal Abstract, BBC.

Written by: Catharine Paddock, PhD
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today