A person’s risk of dementia increases the younger they develop diabetes, research suggests.

Experts say the findings indicate that preventing progression from prediabetes to a diagnosis of type 2 diabetes could mean a substantial reduction in future dementia cases.

Prediabetes is where blood sugar is high but has not yet crossed the threshold for type 2 diabetes.

It is linked with a high risk of progression to diabetes but is also independently associated with other changes in health.

Most people who go on to develop diabetes first pass through this stage of prediabetes.

Among middle-aged adults with prediabetes, 5% to 10% per year go on to develop type 2 diabetes, with a total of 70% of those with prediabetes progressing to diabetes in their lifetime, the researchers say.

Research suggests that up to one third of the UK population may have prediabetes.

To look at the risk of dementia associated with prediabetes, the authors analysed data from people of the Atherosclerosis Risk in Communities (ARIC) study in the US.

According to the study there was a three times greater risk of dementia for those developing type 2 diabetes before the age of 60.

This fell to a 73% increased risk for those developing the condition aged 60-69 and a 23% increased risk for those developing it aged 70-79.

The findings, published in Diabetologia, suggest that at ages 80 or older, developing diabetes was not associated with an increased risk of dementia.

The authors said: “Prediabetes is associated with dementia risk, but this risk is explained by the development of diabetes.

“Diabetes onset at early age is most strongly related to dementia.

“Thus, preventing or delaying the progression of prediabetes to diabetes will substantially reduce the future burden of dementia.”

The study by PhD student Jiaqi Hu and Professor Elizabeth Selvin of the Johns Hopkins Bloomberg School of Public Health, in the US, and colleagues, evaluated the association of prediabetes with dementia risk before and after accounting for the subsequent development of type 2 diabetes.

Among 11,656 people without diabetes to begin with, 2,330 (20%) had prediabetes.

When accounting for diabetes that developed after the baseline period, the researchers found no statistically significant association between prediabetes and dementia.

However, they found that earlier age of progression to type 2 diabetes had the strongest link with dementia.