NEW YORK (Reuters Health) - Type 1 diabetes patients who maintain "tight control" over their insulin levels, which they are encouraged to do to reduce their risk of complications, tend to have relatively frequent episodes of low blood sugar. These patients can now rest easy knowing that these frequent dips in blood sugar are not associated with a decline in mental function, according to a report in The New England Journal of Medicine for May 3rd.

Dr. Alan M. Jacobson, from the Joslin Diabetes Center in Boston, and fellow investigators said this finding, obtained from two studies that spanned nearly two decades, should allay patient concerns about the effect of low blood sugar, also referred to as "hypoglycemia."

The Diabetes Control and Complications trial contained 1441 type 1 diabetics between 13 and 39 years old, who were enrolled between 1983 and 1989.

Half were randomly assigned to intensive therapy, with a goal of keeping blood sugar levels between 70 and 120 mg/dL and hemoglobin levels below normal, but without developing severe hypoglycemia.

The other half were assigned to conventional treatment, which had no set target for blood sugar levels, but had a therapeutic goal of avoiding higher than normal blood sugar levels and episodes of severe hypoglycemia.

After an average follow-up period of 6.5 years, the researchers found no differences between the groups on the results of mental function tests. Instances of severe hypoglycemic events - resulting in coma or seizure -- increased 3-fold in the patients assigned to intensive treatment.

On the other hand, hemoglobin levels remained about normal (7.1 percent) in the intensive treatment group but were too high (9.0 percent) in the conventional-treatment group. Higher levels of hemoglobin were associated with significantly increased incidence of disease of the retina, or "retinopathy," which can cause blindness.

When the study ended, the subjects who had been randomly assigned to the regular care group were switched to the intensive therapy and all subjects were invited to participate in the 12-year follow-up Epidemiology of Diabetes Interventions and Complications study.

After an average follow-up of 18 years, 1144 subjects were re-evaluated. During that time, 896 episodes of coma or seizure were recorded in the intensive treatment group and 459 episodes occurred in the conventional- treatment group.

"Neither the original treatment assignment nor the cumulative number of hypoglycemic events influenced performance" in any aspect of mental, or "cognitive," function," the authors report.

Moreover, scores were "within normal limits of healthy individuals without diabetes."

Jacobson's group cautions that these findings do not suggest that hypoglycemia is entirely harmless, pointing out that sudden hypoglycemic episodes "can be dangerous at the time they occur."

Nevertheless, they recommend intensive diabetes therapy to reduce the long-term risks of retinal disease, kidney disease, neurological disease, heart attack, stroke, or other cardiovascular complications in type 1 diabetes.

SOURCE: The New England Journal of Medicine, May 3, 2007