People with depression and pre-diabetes are nearly three times more at risk of developing dementia in later life, compared to those with neither condition, a landmark longitudinal study has revealed.

While previous research has suggested that there is a link between diabetes, depression and a higher risk of dementia, this is the first time scientists have investigated if the risk is increased if a person has both pre-diabetes and depression.

Scientists followed 3,458 adults over the age of 50 from the English Longitudinal Study of Ageing for up to 10 years. They split the participants into six groups based on the presence of diabetes, pre-diabetes and/or depression. The findings confirm that depression and diabetes were risk factors for dementia but also suggest that those with both depression and pre-diabetes were nearly three times more likely to develop the serious progressive neurological disorder.

Pre-diabetes is a common term used for people who are at a high risk of developing Type 2 diabetes. It is when a person’s blood glucose levels are higher than normal, but not high enough to be diagnosed with Type 2 diabetes. Between 5-10% of people with pre-diabetes go on to develop Type 2 diabetes each year.

Currently 4.6 million people in the UK have diabetes, 90 per cent of these have Type 2 diabetes and 12.3 million people are at an increased risk of developing Type 2 diabetes.
Dr Kimberley Smith, lead author of the study, explained: “There is a lot of evidence that the co-occurrence of depression and diabetes is linked with the development of serious complications of diabetes such as dementia. Our work extends this by also showing that pre-diabetes and depression might also be linked with a greater risk of developing dementia.

“While based on a relatively small number of people, these findings are further evidence of considering the importance of poor mental health in people with prediabetes and diabetes. These preliminary findings will be explored in our future work so we can determine why this association might exist.”

Dr Elizabeth Robertson, Director of Research at Diabetes UK, said: “There is growing evidence linking diabetes and high blood glucose levels to dementia. These new findings suggest an earlier correlation with people at high risk of developing Type 2 diabetes who also have depression.

“More research is now needed to understand why this potential connection could exist, and what can be done to reduce the risk of dementia in as many people as possible. There are steps people can take to reduce their risk of both Type 2 diabetes and dementia. These include maintaining a healthy weight, eating a healthy balanced diet, limiting alcohol intake, avoiding smoking, keeping blood pressure in check and doing regular exercise.”

The findings were announced at the annual Diabetes UK Professional Conference, which brings together world class scientists, researchers and healthcare professionals to present new research and health programmes to tackle the UK’s diabetes crisis.