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NEW YORK (Reuters Life!) - Teenage boys who are heavily into sport get new respect in a Swedish study that found physically active teenagers tend to be smarter than their couch-potato counterparts.
Researchers from the Institute of Medicine at the University of Gothenburg set out to see if aerobic or cardiovascular fitness and muscle strength were associated with brain power and future socioeconomic status.
They analyzed a physical and intelligence snapshot taken of 1.2 million Swedish men born between 1950 and 1976 when they reported for mandatory military duty at age 18.
They also assessed genetic and family influences by looking at the scores of brothers and twins and, over time, the association between all initial scores and measures of success at midlife, including education level and occupation.
The researchers, led by Dr. H. Georg Kuhn, said the results showed a strong positive link between cardiovascular fitness and smarts but not between muscle strength and intelligence measures.
"Male subjects with improved predicted cardiovascular fitness between 15 and 18 years of age exhibited significantly greater intelligence scores than subjects with decreased cardiovascular fitness," Kuhn and colleagues report in Proceedings of the National Academy of Sciences.
The ability to compare twins' scores was another important strength allowing the researchers to remove the "influence of genetic, social and family backgrounds.
Kuhn said with several thousand twins, they were able to show that, on average, the fitter twin also had the higher IQ score.
The researchers said the findings have important implications for the education of young people as increasing, not decreasing, physical education in schools can not only slow the shift toward sedentary lifestyles but also may help address "perhaps intellectual and academic underachievement."
But they said it was still unclear if more active boys are smarter or if smarter boys are more active and more studies addressing causality were needed.
"We cannot assume that fitness per se increases cognitive function, so joining a gym does not by itself make you 'smarter'. But in order for optimal cognitive function/development to take place, regular cardiovascular exercise is needed," Kuhn told Reuters Health.
"There is no reason to assume that this cannot be extrapolated to girls. Women have more or less the same cardiovascular risk factors and therefore benefit from cardiovascular exercise in the same way."
Reporting by Rachael Myers Lowe by Reuters Health, editing by Belinda Goldsmith