Diabetes in middle age can dramatically increase the risk of developing dementia, scientists have warned.
They say the disease causes the mind to age five years faster.
Research shows that middle-aged diabetes sufferrers are at an above-average risk of memory failure and cognitive problems over the following twenty years.
And declining memory, word recall, reasoning and problem solving are all associated with progressing to full blown dementia.
The study revealed that a 60-year-old with diabetes suffers deterioration in their memory to a level of a 65-year-old.
Experts warned people to eat well and exercise regularly to ensure their blood sugar level was under control by the age of 50 or run the risk of developing dementia at 70.
Study leader Dr Elizabeth Selvin of the John Hopkins Bloomberg School of Public Health in the US, said: “If we can do a better job at preventing and controlling diabetes we can prevent the progression of dementia.
“Even delaying dementia by a few years could have a huge impact on the population from quality of life to health care costs.”
Dr Selvin an associate professor of epidemiology went on: ” There is a substantial cognitive decline associated with diabetes, pre-diabetes and poor glucose control in people who have diabetes.
“And we know how to prevent or delay the diabetes associated with this decline.”
The study, believed to be the longest of its kind, was launched in 1987 and followed a cross-section sample of 15,792 middle-aged adults in communities in Maryland, North Carolina, Minnesota and Mississippi.
People were periodically tested for cognitive function, a report published in the journal Annals of Internal Medicine explained.
Researchers compared the amount of cognitive decline normally associated with ageing with the decline found in study participants.
They found there was 19 per cent more decline than expected in participants with poorly controlled diabetes. There were also declines in those with controlled diabetes and pre-diabetes but these were smaller.
Dr Selvin said the results underscored the importance of weight control, exercise and a healthy diet.
Even just losing five to ten per cent of body weight can avert diabetes.
Diabetes leads to raised sugar levels in the blood. This can damage tissues and the vascular system throughout the body.
Research suggests there are many causes of dementia linked to abnormalities in blood vessels in the brain.
Co-author of the research Dr Richie Sharrat said: “There are many ways we can reduce the impact of cerebral blood vessel disease – by prevention or control of diabetes and hypertension, reduction in smoking, increase in exercise and improvements in diet.
‘Knowing that the risk for cognitive impairments begins with diabetes and other risk factors in mid-life can be a strong motivator for patients and their doctors to adopt and maintain long-term healthy practices.” The biggest risk factor for Type 2 diabetes is being obese or overweight.
Diabetes UK figures show nine in ten sufferers need to lose weight. More than half of those with Type 2 diabetes are obese – double the obesity rate in the general population. The condition is now a national emergency in the UK, with 3.2 million people diagnosed. Treatment takes up 10 per cent of the NHS budget.
Dr Laura Phipps, science communications manager at Alzheimer’s Research UK, said: “This study adds to a large body of evidence linking diabetes to thinking and memory problems in later life,.
“It suggests that controlling blood sugar levels in midlife may have long term benefits for our brain health.”
Dr Richard Elliot, Diabetes UK research communications manager said: “High blood glucose and Type 2 diabetes have already been linked to a higher risk of problems with memory and thinking, which can in turn lead to dementia in later life. This robust 20-year study adds to our understanding of that link.
“It suggests that people with higher blood glucose levels and people who have had diabetes for longer are at higher risk.