WASHINGTON -- Tight glycemic control early in the course of type 1 diabetes does not result in later cognitive decline, according to new findings from two studies with an average of 18 years of follow-up data.
"Because of the length of follow-up and extent of cognitive testing, this study strongly supports the safety of intensive diabetes therapy," Dr. Alan M. Jacobson said at the annual scientific sessions of the American Diabetes Association.
The results should allay the serious concerns that have been raised about whether tight glycemic control might lead to more severe hypoglycemic episodes and subsequent decreased cognitive ability, said Dr. Jacobson, head of the behavioral and mental health research section at the Joslin Diabetes Center, Boston.
But the recurrent, severe hypoglycemic events that are more likely to occur with tight glycemic control could still possibly have a negative cognitive effect on older adults, very young children, or those with a longer disease duration, he added.
The results from the multicenter, randomized Diabetes Control and Complications Trial (DCCT) and its continuation in the long-term observational Epidemiology of Diabetes Interventions and Complications (EDIC) study showed that patients who received intensive glycemic control during the DCCT did not have any differences in cognition, compared with conventional treatment, as measured by an extensive test battery involving eight cognitive domains (problem solving, learning, immediate memory, delayed recall, spatial information, attention, psychomotor efficiency, and motor speed), Dr. Jacobson reported.
The 18 years of combined follow-up make the DCCT and the EDIC the largest, longest-term prospective study that has implemented a cognitive assessment of patients with any clinical condition, he said.
Among patients in either group, there were no differences in cognitive functioning in those who had no hypoglycemic episodes, one to five episodes, or more than five episodes.
Control of Hb[A.sub.1c] (glycosylated hemoglobin) values to less than 7.9% similarly showed no significant effects, except in sparing patients from small reductions in psychomotor efficiency and in improving motor speed. The "very modest" declines in psychomotor efficiency and motor speed that were associated with higher Hb[A.sub.1c] values (7.9% or greater) were "consistent with emerging literature on the effects of persistent hyperglycemia on mental and motor slowing," Dr. Jacobson said. …