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Metabolic Syndrome and Cognition in Adolescents
Obesity is not just bad for your body. It can interfere with attention and mental abilities, particularly among the young, whose brains are still developing. That's the message from a new study of children with and without metabolic syndrome.
Metabolic syndrome refers to a group of conditions that are associated with obesity. Its symptoms usually include a mix of abnormalities in weight, high-density lipoproteins (HDL), triglycerides, blood pressure and glucose metabolism. People with metabolic syndrome have an increased risk of developing cardiovascular disease and diabetes and their complications.
The risk of metabolic syndrome generally increases with age, but in the US the epidemic of childhood obesity has produced a young generation who already has this syndrome. A 2006 study showed a prevalence of 8.6% in U.S. children and teens.
Metabolic syndrome is associated with abnormalities in thinking and reasoning skills in adults. This study, by researchers at New York University's School of Medicine, found that overweight younger people with metabolic syndrome show lower overall intelligence than their normal-weight peers.
Methodology The researchers looked at 49 children with and 62 without metabolic syndrome. The groups were similar in the socioeconomic status, school grade, gender and ethnicity of their members. Participants were between ages 14-20 and were excluded if they already had diabetes or other significant medical conditions, had significant learning disabilities, or depression, or used certain medications. Those in the metabolic syndrome group had to show three out of five of the following symptoms: obesity, reduced HDL, elevated triglycerides, elevated blood pressure, and insulin resistance. The participants' IQs and academic achievement were measured with standardized tests and brain structure was evaluated with brain imaging studies.
Results Adolescents who had metabolic syndrome, although they still performed within the normal range, scored lower than their peers in academic and spelling tests and tended to have lower IQs. They also scored lower on tests that measured attention and mental flexibility.
The more of the metabolic syndrome criteria subjects met, the worse their scores on achievement tests; subjects with less pronounced, or fewer metabolic syndrome criteria, had better scores.
Imaging tests revealed that the children with metabolic syndrome showed reductions in the size of their hippocampus, a brain structure connected with memory, and an excess of cerebrospinal fluid (CSF), also indicating an overall reduction in brain volume.
Conclusions It is not clear whether these deficits represent abnormal or delayed development or whether there is damage to previously normal structures. Future studies will be needed to determine this and whether the deficiencies are reversible as weight is lost and metabolic symptoms diminish.
But the key finding remains: structural and functional abnormalities of the brain occur when components of the metabolic syndrome are present even before diabetes develops, painting a concerning picture of the burden placed on developing children simply by being seriously overweight. They also suggest that obesity in childhood can have lifelong implications, affecting academic and work performance as well as health.
The authors conclude that, “Although obesity may not be enough to stir clinicians or even parents into action, these results among youth with metabolic syndrome strongly argue for an early and comprehensive intervention. This is further evidence that obesity in children and teens requires early and aggressive attention to prevent lifelong complications that start as early as childhood and adolescence.
The study is published in the journal, Pediatrics.
September 10, 2012