Tight diabetes control doesn't harm cognitive function, study finds

Researchers led by a team at the Joslin Diabetes Center report in tomorrow's New England Journal of Medicine that tightly controlling blood sugar levels does not impair long-term cognitive function for people with type 1 diabetes.

Type 1 diabetics, whose immune systems destroy cells in the pancreas that make insulin, must monitor the level of sugar in their blood and inject insulin or use an insulin pump to keep down blood sugar. High levels can lead to such complications as blindness, heart disease and kidney failure.

Tight control of blood sugar, however, can unintentionally result in episodes of hypoglycemia, or low blood sugar levels. Hypoglycemia can lead to confusion, coma and convulsions. That has raised concerns that over time, hypoglycemia could cause long-term cognitive problems.

The Joslin study followed 1,441 type 1 diabetics for 12 years, following up on an earlier study of the same participants that showed that after 6 years, diabetics with tightly controlled blood sugar showed the same cognitive function as diabetics on less intensive therapy. The results after 18 years confirmed the earlier findings.

"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," Dr. Alan M. Jacobson, head of Joslin's behavioral and mental health research section and lead author of the study, said in a statement.