Young children up to two years of age who are on the threshold of being overweight or obese tend to test lower at ages 5 and 8 for perceptual reasoning, working memory and overall IQ, compared to same-age lean children, according to new research published in the journal Obesity.
“The first few years of life are critical for cognition development, and we investigated whether early-life adiposity has an impact on cognitive abilities later in life,” said Dr. Nan Li, lead author and a postdoctoral research associate in the department of epidemiology at Brown University.
Studies have shown that adult obesity is associated with lower cognition, as the condition can dysregulate hormones that act in multiple brain regions. But until now, despite the increasing prevalence of childhood obesity, very few studies have focused on whether weight status affects how children learn, remember information and manage attention and impulses.
For the study, Li, along with faculty member Dr. Joseph Braun and their coauthors, focused on a group of children whose weight and height had been recorded at age one and/or age two, and who later underwent a series of cognitive tests.
These children were part of the Health Outcomes and Measures of the Environment study in Cincinnati, which first enrolled pregnant women from 2003 to 2006 and continued to track the children in their early lives.
The researchers focused on the impact of early-life adiposity on neurodevelopment in children. The design of the study allowed them to capture weight status during a period of time when the brain is developing neurological pathways that influence performance and functioning.
As such, the researchers could determine whether a high weight-to-height ratio led to cognitive difficulties, rather than the other way around. In some previous studies, it is difficult to know if excess weight is a result of lower cognition, the authors said. Preexisting low cognitive function could be the root, not the result, of obesity in children, because those children may not have been able to limit their caloric intake or get much physical activity.
Since there were a limited number of children in the study who were overweight or obese, Li said, the researchers grouped the participants into two categories: lean and non-lean. The non-lean group included some overweight and obese children and others who were approaching the threshold for being overweight or obese.
“We were particularly interested in those children who were at great risk of being overweight or obese,” Li said. The researchers wanted to explore whether those at-risk children had lower cognitive test scores compared to lean children, she said.
The children completed a series of tests that evaluated their general cognitive abilities, memory, attention and impulsivity. The researchers found that weight status did not appear to affect performance on some of the tasks, but did significantly impact three of the tests.
“Excess early-life adiposity was associated with lower IQ, perceptual reasoning and working memory scores at school-age,” Li said.
IQ reflects a personâ€™s overall cognitive abilities, while working memory falls under the domain of executive function, which the authors describe as the set of self-regulatory cognitive processes that aid in managing thoughts, emotions and goal-directed behaviors.
“Executive function is associated with academic success in children and is critical for physical health and success throughout life,” the authors wrote.
The researchers say that there are a number of biological mechanisms by which early life adiposity could impact neurodevelopment, including pro-inflammatory cytokines that activate inflammatory pathways in children and adults.
Systematic inflammation may affect multiple brain regions associated with cognitive abilities and has been shown to adversely affect spatial learning and memory in rodents. And the dysregulation of hormones that act on brain regions including the hypothalamus, prefrontal cortex and hippocampus may also have a negative effect on cognition.
The authors pointed out that the sample size of their study was limited and that further studies are necessary to confirm their findings. Future research could also look at the effects of early-life weight status on school performance, attention-deficit/hyperactivity disorder diagnoses and special education use.
Source: Brown University