Sugar and the brain: How blood glucose can affect the brain in children with type 1 diabetes

This study examined the effect of blood glucose on IQ (a measure of general intelligence) in the young diabetic patient.

Glucose (sugar) is essential for normal brain functioning. The brain is very sensitive to the level of glucose in the body, and too much or too little can lead to abnormal function. The brain is developing and changing throughout childhood and adolescence, and may be more sensitive than the adult brain to changes in glucose levels.

Patients with type 1 diabetes often have fluctuations in blood glucose levels. Whether or not these changes have an effect on brain development is not known. Some studies show that diabetes at an early age increases the risk of cognitive deficits (brain functioning below normal levels), but other studies have not seen any connection. Many studies have measured IQ levels in diabetes patients, but these tests have mainly been done in adult patients, or in children who have already lived with diabetes for some time. It is unclear whether IQ levels change over time following the diagnosis of diabetes in a child.

This study compared IQ levels in 95 diabetic children at their diagnosis and twelve years later. IQ levels were also measured in 67 healthy patients. All patients were tested on overall IQ, verbal IQ (the ability to use language skills to solve problems) and performance IQ (the ability to solve non-verbal problems, such as completing a picture). These results were correlated with age of diabetes onset, HbA1c levels (a measure of average blood glucose over 3 months) and number of episodes of hypoglycemia (dangerously low blood glucose levels).

There was a significant decrease in verbal IQ and general IQ in diabetes patients compared to the healthy patients. The verbal IQ scores of patients with diabetes decreased by 7.84 points. The general IQ scores of patients with diabetes decreased by 6.12 points. These were significantly lower than the changes in the healthy patients (decrease of 6.46 in verbal, 5.58 in general IQ).

Patients who were diagnosed with diabetes at a young age (younger than 6 years of age) saw the largest decreases in verbal IQ (10.52 points), performance IQ (9.45 points) and general IQ (11.38 points). Patients with later-onset (older than 6 years of age) diabetes saw a decrease in verbal IQ (6.67 points), but performance and general IQ were not affected. Healthy children saw a similar decrease in verbal IQ. 

Verbal IQ decreased by 11.02 points in patients who had experienced multiple episodes of hypoglycemia with seizures, compared to a decrease of 5.43 points in patients who did not experience seizures. HbA1c levels were not associated with changes in IQ levels.

This study concluded that children with type 1 diabetes, particularly early-onset diabetes and those who experienced seizures, were at increased risk of decreases to IQ. The authors suggest that these patients should be monitored and given extra educational support if necessary.