Intense Diabetes Therapy OK for Brain

May 2, 2007 -- Intensive treatment of type 1 diabetes doesn't appear to worsen long-term mental skills.

That news comes from a study of more than 1,100 type 1 diabetes patients who were followed for 18 years, on average.

The researchers included Alan Jacobson, MD, who heads the Behavioral and Mental Health Research Section at Boston's Joslin Diabetes Center and is a psychiatry professor at Harvard Medical School.

The study, published in The New England Journal of Medicine, "provides further support for the safety of intensive diabetes therapy," Jacobson says in a Joslin Diabetes Center news release.

Type 1 Diabetes Study

The patients enrolled in the study between 1983 and 1989. At the time, they were 13-39 years old.

First, the patients took tests of memory and other mental skills. Next, they were randomly split into two groups.

One group got intensive treatment. Each of those patients wore an insulin pump or gave themselves at least three daily insulin injections.

For comparison, patients in the other group were assigned to give themselves one or two daily insulin injections.

In 1993, intensive therapy was recommended for all participants, "since it had been shown to be highly effective in reducing long-term complications of diabetes," Jacobson's team writes.

At the time, there was no sign of any negative effects on the patients' mental skills, based on a second round of mental skills tests.

But patients who got intensive treatment were more likely to experience episodes of severe hypoglycemia ( low blood sugar) leading to coma or seizure, and the long-term mental effects of those episodes weren't clear. So the researchers extended the follow-up period until 2005, for a total of 18 years.

No Mental Risks Seen

At the end of the 18-year period, the researchers tested the patients' mental skills. Intensive treatment wasn't associated with a substantial decline in test scores.

The patients who got intensive treatment from the study's start weren't more likely to have a big drop in their mental skills test scores during the 18-year period, even though a greater percentage of them (44%) had at least one episode of severe hypoglycemia, compared with 34% of patients who weren't originally assigned to intensive treatment.

That doesn't mean that severe hypoglycemia is harmless.

"While acute episodes of hypoglycemia can impair thinking and can even be life-threatening, type 1 diabetes patients do not have to worry that such episodes will impair their long-term abilities to perceive, reason, and remember," Jacobson says.

The researchers note that they don't have much data on the effects of intensive treatment for very young children with type 1 diabetes. They also have no information on intensive treatment in elderly people or those living with type 1 diabetes for more than 30 years.

In the journal, Jacobson reports serving on medical advisory boards for the drug companies Pfizer and Amylin. Another researcher reports receiving consulting fees from the drug companies GlaxoSmithKline and Amylin, as well as lecture fees from the drug company Eli Lilly.