Some areas of cognitive function, or thinking ability, are impaired in patients with type 1 diabetes, but learning and memory remain intact, Dutch investigators report.

“The magnitude of the cognitive deficits is mild,” report Dr. Augustina M. A. Brands, of University Medical Center, Utrecht, and colleagues, “but even mild forms of cognitive dysfunction might hamper everyday activities.”

The researchers conducted a review of studies that looked at cognitive performance in diabetic patients. Thirty-three studies met the inclusion criteria and were included in the analysis.

As reported in the medical journal Diabetes Care, the team assessed intelligence, learning and memory, psychomotor activity and information processing, attention, cognitive flexibility, visual perception, and language. In addition, they looked into the possible effects of disease variables, including recurrent episodes of low blood sugar levels.

Compared with healthy subjects, those with type 1 diabetes had significantly lowered performance on the intelligence, speed of information processing, and psychomotor efficiency tests. Lowered performance was also observed on visual and sustained attention, cognitive flexibility, and visual perception.

“Our (review) does not support the idea that there are important negative effects from recurrent episodes of severe (low sugar levels) on cognitive functioning,” Brands’ team reports. On the other hand, the eye and nerve problems that can occur in diabetics do “appear to be associated with impaired cognition.”

SOURCE: Diabetes Care, March 2005;28:726-735.