The findings, based on a study of children with Type 1 diabetes, lend support to the American Academy of Pediatrics' advice that children watch no more than two hours of TV daily, said lead author Dr. Hanna Margeirsdottir of the University of Oslo.
Type 1 diabetes is the less common form of the disease and used to be called juvenile diabetes. It is not related to obesity and is caused when the body cannot make insulin, which converts sugar from food into energy. People with Type 1 must take insulin daily and regulate their blood-sugar levels.
Snacking and overeating can increase blood-sugar levels; physical activity can lower them. While TV viewing is often accompanied by snacking, the researchers didn't examine diet or physical activity.
The study results "suggest that encouraging children with Type 1 diabetes to watch less television may be important for improved blood glucose control and better health outcomes," the study authors wrote.
Other experts said the study also might suggest something else. Diabetic children who already have consistently high blood-sugar levels could feel too sick to do much besides watch TV, said Jill Weissburg-Benchell, a psychologist and diabetes educator at Children's Memorial Hospital in Chicago.
"It's very clear that there is a relationship. Now the question is: What underlies that relationship," she said.
Results of the Oslo research will appear in the June edition of the journal Diabetes Care.
The study involved 538 children with an average age of 13. In Norway, about 25,000 people have Type 1 diabetes. In the United States, there are 3 million with the condition and about 30 million worldwide.
The study evaluated results of a routine test that measured average blood-sugar control over three months. There was a continuous increase in the level of blood sugar with every hour of TV watched, rising to the highest level for those who watched at least four hours daily.
The results didn't surprise Chicago diabetes educator Monica Joyce, who founded a basketball camp for diabetic children.
Campers typically are asked how much TV they watch and are taught "they can get much better blood sugars if they're active," Joyce said.
If the researchers' theory is right, turning off the TV could be added to a list of remedies "that are very low-cost to the health care system," said Dr. Francine Kaufman, head of a diabetes program at Children's Hospital in Los Angeles.
"This has got to be the social norm that it's just not acceptable for kids to be baby-sat by TV," she said.