A Swedish study involving 1.2 million men reveals a link between a strong cardiovascular system in young adulthood and IQ and intelligence later in life.
Young adults who are physically fit have higher IQs and are more likely to pursue higher education, according to Swedish researchers. Study results showed a clear link between good physical fitness and better results on the IQ test. The strongest links were for logical thinking and verbal comprehension. But only fitness played a role in the IQ results, not physical strength.
“Being fit means that you also have good heart and lung capacity and that your brain gets plenty of oxygen,” said Michael Nilsson, Professor at the Sahlgrenska Academy and Chief Physician at the Sahlgrenska University Hospital in Gothenburg, Sweden. “This may be one of the reasons why we can see a clear link with fitness but not with muscular strength. We are also seeing that there are growth factors that are important.”
The study involved 1.2 million Swedish men born between 1950 and 1976 who were enlisted for military service at age 18. Of these, 268,496 were full-sibling pairs, 3,147 twin pairs, and 1,432 monozygotic twin pairs. The researchers analyzed physical fitness and IQ test results collected during conscription examinations and compared them to national databases. Results were published in the December 8, 2009, Proceedings of the National Academy of Sciences.
According to the researchers, cardiovascular fitness, as measured by ergometer cycling, was positively associated with intelligence after adjusting for relevant confounders. Similar results were obtained within monozygotic twin pairs. In contrast, muscle strength was not associated with cognitive performance. Cross-twin, cross-trait analyses showed that the associations were primarily explained by individual specific, nonshared environmental influences (≥ 80%), whereas hereditability explained less than 15% of covariation. “Cardiovascular fitness changes between age 15 and 18 predicted cognitive performance at age 18,” reported lead author Maria A.I. Åberg, MD, PhD, and colleagues.
The researchers also compared the results from fitness tests during national service with the socio-economic status of men in later life. Those who were physically fit at age 18 were more likely to go into higher education, and many secured more qualified jobs.
“These data substantiate that physical exercise could be an important instrument for public initiatives to optimize educational achievements, cognitive performance, as well as disease prevention at the society level,” Dr. Åberg and colleagues concluded.