The link between type 2 diabetes and poorer cognitive functioning may be due to wide swings in post-meal (postprandial) blood sugar (glucose) levels, an Italian study suggests.
Researchers studied 156 older people with type 2 diabetes. The participants were between the ages of 60 and 78 and were taking either repaglinide (Prandin) or glyburide (DiaBeta and other brands) for their diabetes. Those whose glucose levels varied widely after they ate performed worse on cognitive tests than those who maintained tighter control over their blood sugar. This association persisted after the researchers adjusted for such factors as physical activity, obesity, and blood pressure. The results also showed that repaglinide was associated with less postprandial glucose variability than glyburide.
A number of previous studies have examined the link between type 2 diabetes and impaired cognitive function. Diabetes and poor overall glucose control have also been found to increase the risk of developing dementia. These results strengthen the argument that better control of blood sugar benefits the brain -- just as it benefits the heart, eyes, and kidneys. This study was reported in the journal Neurology (Volume 67, page 235).
Tighter Blood Sugar Control Improves Memory
People with type 2 diabetes have a higher than average risk of memory loss as they age, according to a study reported in the journal Diabetes Care (Volume 29, page 345). But can improving control of blood glucose safeguard memory?
To find out, researchers enrolled 145 men and women with type 2 diabetes in a six-month study. All of these diabetes patients were initially taking metformin (Glucophage) yet had modestly elevated HbA1c levels. (HbA1c is a measure of blood sugar control over time.)
Each diabetes patient then added a new diabetes drug to his or her daily regimen, either rosiglitazone (Avandia) or glyburide (DiaBeta and other brands). The diabetes patients took various tests of memory and mental speed at the beginning and end of the study.
After six months, study subjects taking either drug had lowered their HbA1c to below 8%, on average. (The goal is below 7%.) When retested, members of both groups made 25–31% fewer errors in tests designed to measure working memory, the short-term memory needed to perform daily tasks.
For both rosiglitazone and glyburide, the magnitude of memory improvement was related to the extent of blood glucose control. This study also offers strong evidence that maintaining better blood glucose control leads to sharper wits -- a fact worth remembering.
