Lain Frame of Diabetes U.K. stated that, "This study reinforces previous evidence which suggests that poorly controlled diabetes affects the functioning of the brain.... We already know that Type 2 diabetes increases the risk of developing Alzheimer's disease, which is a type of dementia, and this research adds another piece to a very complex jigsaw puzzle."

Type 2 diabetes is marked by unusually high blood sugar levels due to the body's acquired insensitivity to the sugar-regulating hormone insulin.  Excessive doses of insulin or other diabetes drugs may push blood sugar levels too low, resulting in a hypoglycemic episode -- or "hypo" -- in which the brain is starved of the glucose it needs to function.

Symptoms of hypos include blurred vision, dizziness, elevated heart rate, hunger, fatigue, sweating and weakness.

Researchers at the University of Edinburgh, UK, tested 1,066 Type 2 diabetes patients between the ages of 60 and 75 on various cognitive abilities including concentration, logic and memory. They found that the 113 participants who had experienced severe hypos in the past scored significantly lower on tests of vocabulary and general mental ability.

Lead researcher Jackie Price noted that the study was correlative, and could not prove whether hypos caused the lessened cognitive ability.

"Either hypos lead to cognitive decline ... or cognitive decline makes it more difficult for people to manage their diabetes, which in turn causes more hypos," Price said. "A third explanation could be that a third unidentified factor is causing both the hypos and the cognitive decline."

Study conducted by researchers from the University of Edinburgh,UK, and presented at a conference of the nonprofit Diabetes U.K., Oct 2009.