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Diabetes and the risk of dementia

Diabetes is a confirmed risk factor for dementia. Learn about some of the research into diabetes and dementia.

Does diabetes increase the risk of dementia?

A hormone called insulin controls blood sugar levels. Diabetes is when not enough insulin is produced, or the body’s cells do not respond to insulin properly leading to high blood sugar levels. There are two forms of diabetes:

  • Type 1 diabetes – a condition people are born with that causes the body’s immune cells to wrongly attack the cells that make insulin.
  • Type 2 diabetes – a condition people develop during their lives when the body starts to produce less insulin or cells don’t respond to the insulin as they should – known as insulin resistance.

Research shows that type 2 diabetes increases a person’s risk of developing dementia. Dementia risk also increases with the length of time someone has diabetes and how severe it is. However, it is important to note that diabetes is only a risk factor and does not mean that a person with diabetes will go on to develop dementia.

In people with type 1 diabetes. severe blood sugar highs and lows are also associated with increased risk of developing dementia.

How to reduce the risk of dementia

A lifelong approach to good health is the best way to lower your risk of dementia.

There are some lifestyle behaviours with enough evidence to show that changing them will reduce your risk of dementia.

Reduce your risk of dementia

Reducing your risk of diabetes

As you get older, you are more likely to develop certain health conditions, including diabetes. To manage this, speak to your GP about going for a health check.

Eating a healthy, balanced diet may reduce your risk of type 2 diabetes. No single ingredient, nutrient or food can improve health by itself. Instead, eating a range of different foods in the right proportions is what makes a difference. This is known as a ‘balanced’ diet.

By eating a balanced diet you are more likely to get all the nutrients you need to stay healthy. The NHS Eatwell guide shows what food groups make up a balanced diet and roughly how much of each is needed to stay healthy.

Research into diabetes and dementia

People with diabetes have about 60% increased risk of developing dementia compared to those without diabetes. This was from a review that brought together the findings from 14 studies.

Studies also suggest that the risk of dementia increases with longer durations of diabetes. Although another study showed that dementia diagnosis decreases within the first two years of diabetes diagnosis and then increases after that.

There are reasons that diabetes may affect dementia risk:

  • Diabetes is linked to other dementia risk factors – so someone with diabetes is more likely to have high blood pressure, high cholesterol and obesity.
  • Some of the changes that occur in Alzheimer’s disease are similar to those in diabetes. In both, nerve cells in the brain may become resistant to the effect of insulin. This may lead to the build-up of amyloid and tau proteins in the brain. Alzheimer’s disease is sometimes unofficially known as type 3 diabetes.

Does diabetes treatment help dementia risk?

Less is known about the difference in dementia risk between treated and untreated diabetes.

The effect of different diabetes medications on dementia and thinking skills is unclear as little research has been done in this area. The majority of studies have shown that people taking the diabetes drug metformin are less likely to have memory and thinking problems or dementia compared to those on other medicines or those who are untreated.

However, some studies seem to suggest that metformin has no effect or may even increase dementia risk. So more research is needed to conclusively show the effect of metformin.

Insulin resistance (as occurs in diabetes) can also affect the brain. Drugs are being developed for Alzheimer’s disease that work in a similar way to diabetes drugs that tackle insulin resistance.

Further reading

Despite the challenges that diabetes and dementia can bring, Ernie is determined to stay positive.

Find out more

Find out about the causes of diabetes, when to see a GP and how to live with diabetes.

Find out more

Diabetes UK takes you through everything you need to know about the condition.

Find out more

Last reviewed: December 2023

Next review: December 2025