Nov. 4, 2011 -- Children who are overweight and don't get enough sleep may have a harder time learning, and those with learning difficulties may be at higher risk for obesity and sleep problems, new research suggests.
The study found that a child's weight, sleep problems, and ability to learn are all connected, with each influencing the other.
Although one expert says the study raises some interesting questions about the relationship of obesity, sleep, and intelligence, it's far too soon to even suggest that intelligence levels alone play a role in obesity or sleep problems.
It is widely recognized that obesity increases the risk for sleep apnea and related conditions, known collectively as sleep-disordered breathing (SDB).
Chronic lack of sleep has also been shown to have a negative impact on learning. But the new study is among the first to examine the interaction of obesity, lack of sleep, and intelligence in elementary school children.
Study researcher Karen Spruyt, PhD, of the University of Chicago Pritzker School of Medicine, says sleep problems are often overlooked in children with weight or learning problems.
Weight, Sleep, and Learning Connected
The study included 351 elementary school children living in Louisville, Ky. Their average age was 8.
None of the children had a diagnosed learning disability that warranted a special-learning designation in school and none was taking ADHD drugs.
The children underwent standardized intelligence testing, with emphasis on traits associated with learning, such as memory, working memory, planning, problem solving, and attention, Spruyt tells WebMD.
They also spent a night in a sleep lab where they were evaluated for SDB.
Spruyt and colleagues relied on a widely used analysis technique known as structural equation modeling to examine the interaction between body weight, sleep quality, and learning.
The model showed that each variable influenced the other:
- Poor sleep increased a child's risk for both obesity and lower scores on the learning ability tests.
- Obesity increased the risk for breathing-related sleep issues and lower learning ability scores.
- Lower learning ability scores influenced the risk for obesity and sleep problems.
Because all the children in the study were considered developmentally normal, the study does not address the impact of obesity and sleep problems on kids with diagnosed learning disabilities, Spruyt says.
Checking for Sleep Problems
Dietitian Nancy Copperman, MS, RD, has been working with overweight and obese children and their families for two decades.
The director of public health initiatives at the North Shore-LIJ Health System in Great Neck, N.Y., Copperman says the negative impact of obesity on sleep and the link between poor sleep and higher body weight is widely recognized.
But she adds that the impact of poor sleep and poor fitness on learning among children is only now beginning to be emphasized.
"Sleep should definitely be one of the things that is looked at when a child is being assessed for poor academic performance," she says.
She says the study's suggestion that intelligence may be protective against obesity and sleep problems needs to be confirmed.
"Many kids who are normal weight have learning issues and many overweight kids do not," she says. "I don't know that we can say that higher cognitive ability is directly linked to obesity."