Repeated exposure to the low blood sugar levels caused by poorly controlled diabetes may damage the brain's cognitive function, according to a study conducted by researchers from the University of Edinburgh and presented at a conference of the nonprofit Diabetes U.K.
"This study reinforces previous evidence which suggests that poorly controlled diabetes affects the functioning of the brain," said Iain Frame of Diabetes U.K. "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 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."
According to the World Health Organization, an estimated 171 million people around the world are diabetic, with the number set to double by 2030. In the United States, 24 million people have been diagnosed with diabetes, 5.7 million are undiagnosed and 57 million are prediabetic.