It should be no great surprise that type 2 diabetes damages the brain.

Much of the attention – in public health educatioon– goes to the damage done by sugar spikes to the eyes, hands and feet, and heart.

Sure, uncontrolled spikes can send you blind, and cause you to have your feet cut off. And kill you with a heart attack or stroke. Not great.

But those same spikes occur in the brain, damaging nerves and blood vessels.

As this damage accumulates, you may develop problems with memory and learning, unstable mood, and hormonal changes. Eventually dementia may catch up with you.

Read more about diabetes and cognitive decline here.

Any good news?

Yes! The body has a warning signal that you’re likely to crash through into type 2 diabetes (T2D), which can be avoided.

This is the main finding of a new big study from the Johns Hopkins Bloomberg School of Public Health in Baltimore.

The warning is inherent in pre-diabetes, “an intermediate stage of high blood sugar, where blood sugar is high but has not yet crossed the threshold for T2D”.

Most people who develop T2D first pass through this ‘window’ of prediabetes.

This has led researchers to wonder if prediabetes, in itself, also carried an increased risk for dementia later in life.

But no, it doesn’t.

Short version of the study

The Johns Hopkins team looked at data from 11,656 participants without diabetes; however, 20 per cent had pre-diabetes.

These people were aged 45 to 64 years when they first enrolled in the study.

In five sessions, spread over about 20 years, the participants had their blood sugar measured, and underwent a series of cognitive and neuropsychological tests.

In a final follow up, about 30 years after enrolling in the study, the researchers looked at who had developed prediabetes, who of these developed T2D, and subsequently dementia.

The findings

The researchers found “no significant association” between prediabetes and dementia.

This means if your prediabetes is reversed (which can be done easily enough via lifestyle interventions) you can avoid T2D and dementia.

As the researchers put it: “While prediabetes itself does not seem to be associated with dementia, people who develop diabetes must pass through this prediabetes window, so preventing progression from prediabetic state to a diagnosis of type 2 diabetes could mean a substantial reduction in future dementia cases.”

A nasty finding

The researchers also looked at whether the age you’re diagnosed with T2D impacts the risk of dementia.

They found a three-times increased risk of dementia for those who developed T2D before the age of 60.

This fell steeply to a 73 per cent increased risk for those developing T2D in people aged 60 to 69 years.

For people developing T2D when aged 70 to 79, the risk of developing dementia dropped again, to 23 per cent.

At age 80 years or older, developing T2D was not associated with an increased risk of dementia.