Stopping prediabetes progress could curb dementia

Diabetes increases dementia risk, but there's no additional risk for patients with prediabetes.

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Diabetes increases the risk of dementia, but not if the patient doesn’t progress beyond prediabetes, US research suggests.

“Earlier age of onset of diabetes was associated with a substantially greater risk of dementia. Among people with prediabetes, preventing and delaying the progression to diabetes is likely to reduce dementia burden,” the researchers wrote in Diabetologia.

The large population-based cohort study of almost 12,000 middle-aged adults found that around 3000 people developed diabetes and 2300 developed dementia in the two-decade follow-up.

One in five study participants had prediabetes, but four in five people with the condition didn’t know they had it.  

More than two in three patients with prediabetes went on to develop type 2 diabetes in their lifetime, the authors found, and they were twice as likely to develop diabetes as those without prediabetes.

The study found that people who developed type 2 diabetes before age 60 had triple the risk of developing dementia compared with those without type 2 diabetes. But this elevated risk dropped significantly as the age of diagnosis increased (73% with age of onset between 60-69 years, and 23% in 70–79-year-olds).

Those diagnosed as having type 2 diabetes over age 80 did not have an increased risk of dementia.

Although prediabetes has previously been associated with increased incidence of dementia, it has been unclear whether this link could be explained by the intervening onset of type 2 diabetes.

Associate Professor Sof Andrikopoulos, spokesperson for Diabetes Australia, said that although the mechanism linking diabetes and dementia was not fully understood, “clearly presence of high glucose levels is the driving force here.”

As a result, diabetes screening could play a role in combatting dementia.

“It is a matter of identifying those people at the highest risk; the highest BMI with other associated issues – high blood pressure, high blood lipids, maybe sleep apnoea, maybe high sugar levels (prediabetes), or cardiovascular risk. Identifying that population and then trying to provide support for that higher risk population… Clearly, we are not doing [this].”

But screening alone wasn’t the answer, Professor Andrikopoulos said.

“The question isn’t about screening. That’s the easy bit. The question is; once you find somebody that by definition has prediabetes, then what do you do?” he questioned.

“GPs are run off their feet. It can’t be [the responsibility of] GPs, unless we increase the capacity. We need to find alternative models.”

“We need investment and a clear referral pathway [for enrolment into lifestyle programmes].We achieve [this] by having a better, more coordinated health system.”

In concurrence with the authors, Professor Andrikopoulos stressed the effectiveness of lifestyle interventions in managing diabetes as well as potentially preventing progression of prediabetes to diabetes.

“The most effective thing you can do is lifestyle modification… Lifestyle [changes] have almost double the effect on slowing down of progression of diabetes [compared to metformin].”

“A lot of people want the magic bullet. ‘Give me something so this goes away’. It’s not that easy. If it were that easy, we wouldn’t have an epidemic of diabetes.”

Diabetologia 2023, online 25 May