Aging Intelligently

Human intelligence is highly variable among people, but only somewhat variable across a person’s lifespan. New research points to genes as the keys to maintaining intelligence as we age.

The study, published in Nature, analyzed the genes of nearly 2000 people to assess their intelligence in childhood and old age. The participants, all part of the Lothian Birth Cohorts, took general intelligence tests at age 11 and again at age 65, 70, or 79. The researchers simultaneously analyzed genome-wide single nucleotide polymorphisms in the individuals. Overall, genes accounted for 24% of the change in intelligence that occurred across a single person’s lifespan. The researchers also concluded that the correlation between intelligence in childhood and intelligence in adulthood was 0.62. (A similar evaluation of the same cohort reported that intelligence in childhood is actually protective of intelligence later in life.)

Differences in intelligence are related to important life outcomes: education, occupation, income, health, and lifespan. And, so far, most data has pointed to a strong heritability of intelligence. But, the individual genes that account for intelligence have not been identified, and most studies point to many small genetic influences, rather than one large one, that have an additive effect on intelligence.

This leaves lots of “wiggle room” in identifying who the intelligent people are and how they got that way. It seems that nature and nurture play a role, not only in intelligence itself, but in maintaining intelligence across the lifespan. Clearly, genetics does not explain it all; there must be environmental contributions to establishing and maintaining intelligence. Genes are not the final determinant of intelligence and mental capability, and factors such as eating a healthy diet, engaging in regular exercise, staying mentally stimulated, and maintaining an active social life can help prevent changes in intelligence as a person ages.

With this new research, the door is open for scientists to identify the actual genetic components of intelligence, and possibly develop screening tests and early interventions to combat genetically-influenced declines in cognitive abilities. But, for now, do not be defined by your genes; intelligence is what you do with your genes. In use-it-or-lose-it fashion, you will only remain as sharp as the books you read, the places you travel, or the mental challenges you accept.

References

Davies G, Tenesa A, Payton A, Yang J, Harris SE, Liewald D, Ke X, Le Hellard S, Christoforou A, Luciano M, McGhee K, Lopez L, Gow AJ, Corley J, Redmond P, Fox HC, Haggarty P, Whalley LJ, McNeill G, Goddard ME, Espeseth T, Lundervold AJ, Reinvang I, Pickles A, Steen VM, Ollier W, Porteous DJ, Horan M, Starr JM, Pendleton N, Visscher PM, & Deary IJ (2011). Genome-wide association studies establish that human intelligence is highly heritable and polygenic. Molecular psychiatry, 16 (10), 996-1005 PMID: 21826061

Deary IJ, Johnson W, & Houlihan LM (2009). Genetic foundations of human intelligence. Human genetics, 126 (1), 215-32 PMID: 19294424

McDonald PT, & Schmidt CD (1990). Differential survival of male and female partially resistant horn flies (Diptera: Muscidae) on steers treated with permethrin. Journal of economic entomology, 83 (5), 1715-7 PMID: 2258510

Gow AJ, Johnson W, Pattie A, Brett CE, Roberts B, Starr JM, & Deary IJ (2011). Stability and change in intelligence from age 11 to ages 70, 79, and 87: the Lothian Birth Cohorts of 1921 and 1936. Psychology and aging, 26 (1), 232-40 PMID: 20973608

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