"Use or miss" is the wisdom received when it comes to cognitive ability. But is there any truth in this old mountain range? Our latest study suggests that it depends on how much you have to get started.
Previous observational studies that examined the effect of mentally stimulating activities, such as puzzles, on cognitive ability, largely supported the "use or miss" hypothesis. However, these studies have often been based on time snapshots – so-called cross-sectional studies. To find out if there really is a connection between lifelong mental involvement and cognitive ability in old age, it is necessary to follow people's mental habits and abilities throughout life.
For our study, reported in BMJ, we wanted to know whether mental involvement protects against cognitive decline, or whether those with a cognitive advantage get more involved, giving the impression that such behavior is responsible for their superior abilities. To answer these questions, we needed to work closely with the participants in our study and measure their intellectual abilities over and over again and compare their abilities with their early life performance.
Scotland is unique because in 1947 almost all 11-year-olds took the same mental ability test. The Scottish Board of Education Research preserved these records and in 1998 allowed us to contact the survivors who took the test.
We tested people living independently, without dementia, on up to five occasions, over 15 years. Demographic, clinical, questionnaire, and psychological data were recorded at all assessments and related to changes in performance on repeated verbal memory and mental velocity tests.
Our results are remarkable because they include child intelligence data from a rare historical intelligence survey. They showed that at the end of life, levels of mental capacity are strongly linked to the current levels of engagement in problem solving.
Our study was able to explain children's intelligence and education and revealed that the rate of decline in end-of-life cognition did not differ between people who reported different levels of involvement. However, levels of engagement were associated with performance at entry, at 64 years.
Child intelligence was associated with intellectual engagement, which raises the question: do smarter people engage more or are smarter because they engage? If the latter were true at the end of life, then we expect some influence on the rate of decline.
We have shown that intellectual involvement in this group of people without dementia is not related to subsequent rates of cognitive decline. But the involvement is linked to the intellectual gain gained from infancy to the end of middle age when we begin to test them. In other words, doing puzzles and other intellectually engaging things throughout your life improves your IQ, so that when the inevitable cognitive decline sets in later in life, you have a higher point to begin with. The rate of decline is the same for everyone, regardless of involvement levels.
At this stage, we can predict how lifelong intellectual engagement contributes to the protection not falling below some intellectual threshold where you would be considered harmed. This is achieved by starting from a higher point.
Our findings are consistent with comparative studies that accompanied elderly individuals over 50 years of age. We have identified problem resolution as being of specific importance. This suggests that interventions to increase resilience to aging should include problem solving components such as reading complex novels, crossword puzzle solving, and practicing a musical instrument.
Roger Staff, Senior Honorary Professor in Aging, University of Aberdeen; Lawrence Whalley, Emeritus Professor of Mental Health, University of Aberdeenand Michael Hogan, senior professor of psychology, National University of Ireland Galway
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