The risk of developing dementia increases in persons with type 2 diabetes who develop glucose resistance earlier in their lives, a significant study has revealed.

New research published in Diabetologia, the journal of the European Association for the Study of Diabetes, shows an association between type 2 diabetes and developing dementia in later life -- with the risk of dementia increasing the earlier a person develops the disease.

The study investigated the association between prediabetes and dementia. Prediabetes is an intermediate stage of high blood sugar, where blood sugar is high but has not yet crossed the threshold for type 2 diabetes.

"Prediabetes is associated with dementia risk, but this risk is explained by the development of diabetes. Diabetes onset at an early age is most strongly related to dementia," said the study by Jiaqi Hu and Professor Elizabeth Selvin of the Johns Hopkins Bloomberg School of Public Health in the US.

To reach this conclusion, the authors analysed data from participants of the Atherosclerosis Risk in Communities (ARIC) study. Those enrolled were aged 45-64 years in 1987-1989 and from four US counties.

The cognitive function assessments incorporated data from a scoring system involving three cognitive tests. Among 11,656 participants without diabetes at baseline, 2,330 (20 per cent) had pre-diabetes.

They found that the earlier age of progression to diabetes had the strongest association with dementia -- 3 times increased risk of dementia for those developing diabetes before age 60.

It fell to a 73 per cent increased risk for those developing type 2 diabetes aged 60-69 years and 23 per cent increased risk for those developing diabetes aged 70-79 years.

At ages 80 years or older, developing type 2 diabetes was not associated with an increased risk of dementia. "Preventing or delaying the progression of prediabetes to diabetes will substantially reduce the future burden of dementia," the authors noted.