The Link Between Blood Glucose and Cognitive Function

It has long been established that having diabetes raises your risk for dementia (impaired mental functioning) as you age. As we’ve covered here at DiabetesSelfManagement.com, previous studies have found that both diabetes and depression, as well as having diabetes complications, can raise this risk.

But a recent study has discovered something new and striking. Using several different methods for cognitive assessment, the researchers found that higher blood glucose levels predict greater cognitive decline in the future — even if your levels aren’t high enough yet to constitute diabetes.

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How the study was conducted

Published in January 2018 in the journal Diabetologia, the study included over 5,000 participants, with an average age of 66, who took part in the English Longitudinal Study of Ageing (ELSA) in the United Kingdom. Cognitive function was first assessed in 2004 or 2005, then every two years until 2014 or 2015.

A few different tests were used to assess cognitive function. To test their memory, participants were tested on immediate and delayed recall of 10 different unrelated words. Executive function was measured by having participants name as many animals as they could in a minute, and orientation was measured by questions about the year, month, date, and day of week.

Initial HbA1c levels (a measure of long-term blood glucose control) of participants ranged from 3.6% to 13.7% — from normal to very high blood glucose levels.

Compared with participants with normal HbA1c levels, those with prediabetes (an HbA1c level between 5.7% and 6.4%) and diabetes (HbA1c of 6.5% or above) experienced greater cognitive decline, in proportion to their HbA1c level. This was true after controlling for a number of factors, including age, sex, body-mass index (BMI), and a number of different health conditions.

What the results mean

This study confirms that even slightly elevated blood glucose levels will lead to greater cognitive decline over time, compared with normal levels, says Wuxiang Xie, the study’s lead author and a clinical researcher at the Peking University Health Science Center in Beijing, China.

Because of this, ”It’s important to take on early management, even before diabetes,” of blood glucose levels, according to Xie.

The good news is that even if you have diabetes already, lowering your HbA1c level may help limit future cognitive decline.

”Optimal glucose control that maintains a relatively low HbA1c level might help to alleviate subsequent cognitive decline,” Xie says, although he cautions that “the effects of intense glucose management on cognitive decline are still under debate.”

So while it’s a good idea to focus on blood glucose control to ward off dementia, more research is ultimately needed to determine what the most effective approach might be.

”I think it’s essential to reveal the mechanisms beneath this association between diabetes and cognitive decline,” says Xie. “Only in this way we can finally figure out ways to effectively ward off those complications of the disease.”

Want to learn more about diabetes and cognitive health? Read “Keeping Alzheimer’s Disease at Bay,” “Nine Tips to Keep Your Memory With Diabetes,” and “Memory Fitness: How to Get It, How to Keep It.”

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