Tight Control of Diabetes Doesn’t Slow Cognitive Decline

Older people with type 2 diabetes are at higher risk of cognitive impairment then non-diabetics.  It’s accepted that tight control of blood sugar levels, as opposed to standard control, helps ward off the complications of diabetes involving the eye (retinopathy), kidneys (nephropathy), nerves (neuropathy), and cardiovascular events (atherosclerosis etc.).  The results for slowing the risk of cognitive impairment have proved less certain, so it’s appropriate that a definitive study has been completed and published; it can be found in the online version of The Lancet Neurology.      

This study was the Memory in Diabetes (MIND) part of the Action to Control Cardiovascular Risk in Diabetes (ACCORD) trial.  Almost 3,000 patients between 55 and 80 with type 2 diabetes and at high risk for heart disease were enrolled.  They were randomly assigned to have either intense blood-sugar lowering or standard treatment; with the intensive treatment the target was an HbA1c level of below 6.0%, whereas standard treatment aimed at a level of 7.0% to 7.9% HbA1c.  Cognitive function was measured using the Digit Symbol Substitution Test at baseline, 20, and 40 months.   A subset of the patients had a magnetic resonance imaging (MRI) brain scan at baseline and 40 months; this was done to allow assessment of changes in total brain volume.

Before the planned endpoint of the study it was found that mortality in the intensive control group patients was increased, so the participants in this group were switched to standard therapy.  This resulted in slightly fewer patients who completed the study in the intensive control group than in the standard care group – 1,378 vs. 1,416 patients.

There was no significant treatment difference between the 40-month cognitive ability scores for the two groups.  However, the intensive control group had a significantly greater average total brain volume than the standard treatment group. 

The disparate study findings are interpreted by the investigators as follows: “Although significant differences in total brain volume favored the intensive treatment, cognitive outcomes were not different.  Combined with the non-significant effects on other ACCORD outcomes, and increased mortality in participants in the intensive treatment group, our findings do not support the use of intensive therapy to reduce the adverse effects of diabetes on the brain in patients with similar characteristics to those of our participants.”   

This advice is in concert with other more recent reports that intensive control methods are not helpful, and may be harmful, when used in older type 2 diabetics.