Lowering diabetics’ blood sugar below current recommended levels doesn’t prevent cognitive decline, according to a 3,000-patient study that is part of a larger trial known as ACCORD.
Insulin is important to normal brain functioning and reduced levels have been suspected to contribute to progression of Alzheimer’s disease or other types of dementia. (The results of a recently published preliminary trial involving 104 adults with mild cognitive impairment or Alzheimer’s disease suggest inhaled insulin might prevent cognitive decline.)
In the new study, published in the Lancet Neurology, diabetics’ blood sugar was controlled either to the level consistent with current American Diabetes Association standards, or more intensely, to an even lower level.
After 40 months, there wasn’t a difference in the rate of cognitive decline between the two groups, though those whose blood sugar was controlled more intensely had larger brain volumes. Smaller brain volume is linked to cognitive decline.
The researchers are continuing to follow the patients for several years after the end of treatment to see if differences in cognitive ability between the two groups emerge later on.
For clinicians and patients, the take-home message is that “you need to follow the standard guideline for control of diabetes,” according to Lenore Launer, chief of the neuroepidemiology section at the National Institute of Aging. Still more research is needed to identify the optimal treatments for physical and brain health, she says.
But in general, “what’s good for your heart is good for your brain,” she says. That suggests people should also watch their weight, get exercise and keep tabs on other cardiac risk factors, including blood-sugar levels.