Nov. 4, 2011 -- Obesity, sleep apnea and behavior and learning difficulties can cause significant dysfunction in children, but a new study suggests these three problems interact with one another, exacerbating the effects of each individual problem.
Researchers at the University of Chicago's Comer Children's Hospital and Pritzker School of Medicine performed sleep, cognitive and body weight tests on more than 350 healthy, normally developing children ages 6 to 10, and found a complex relationship between the three factors.
"Cognitive functioning in children is adversely affected by frequent health-related problems, such as obesity and sleep-disordered breathing," the authors wrote. "Furthermore, poorer integrative mental processing may place a child at a bigger risk for adverse health outcomes."
On the other hand, "good cognitive abilities may be protective against increased body weight and sleep-disordered breathing," said Karen Spruyt, the study's lead author. "If the brain can function optimally, it can help protect against the clinical manifestation of disease."
This study, she said, published this week in the American Journal of Respiratory and Critical Care Medicine, is one of the only ones to evaluate the relationship between obesity, sleep apnea and cognitive ability at the same time in either children or adults.
Past research has looked at them separately. For example, studies have found that the mental functioning of obese people with sleep apnea is impaired, but these studies didn't look at the reverse relationship. Other research has found a link between both body weight and sleep disorders, and a study published in January found a link between a lack of sleep and childhood obesity.
The new study findings suggest, Spruyt explained, that when targeting obesity in children, clinicians should also screen for sleep apnea and cognitive impairment, because improving one of these variables could also lead to improvement in the others.
"Keep in mind all the interplays that are there," she said. "Don't discard any of the confounding factors."
Exact Nature of Relationship Not Yet Known
"The conclusion of this study is that it's not as simple as one of these factors causes the other," said Dr. David Rapoport, director of the sleep medicine program at the New York University School of Medicine in New York, who was not involved in the research. "But it's not yet clear exactly what the relationship is."
Rapoport said that treating obesity will generally take care of sleep apnea as well, but this study highlights the importance of taking the other problems into account too.
"Just treating sleep apnea, for example, may not improve cognitive function, because obesity may be involved as well."
But he also explained that childhood obesity is extremely difficult to treat, which is why the outcomes associated with it, such as sleep apnea and diabetes, are often targeted first.
"We try to treat obesity, but we fail," he said. "In the past, we would have said to put the child on a diet, but the success rate is miserable."
Research has not evaluated the interaction of these three factors in adults, in part because it's more difficult to measure cognitive function in adults. Children's abilities, on the other hand, can be assessed in school.
In addition, Spruyt explained that children's minds are still developing during the early school years, and they are more vulnerable to the health effects of obesity and sleep apnea.
Spruyt also said the next logical step in the research would be to try to determine precisely how obesity and sleep apnea affect the brain.
"This is a stepping stone for imaging studies," she said. "Imaging studies would help to localize what brain areas are impacted."