Adults with diabetes may find their mental abilities slowing down soon after the disease appears, a study suggests.

Researchers at the University of Alberta found that semantic speed and higher functions such as planning, organising and paying attention to details were noticeably worse in patients with type 2 diabetes than in healthy adults.

As Britain’s diabetic population continues to rise sharply, the findings mean that millions of people could be in danger of progressive mental slowing. The study, published in the journal Neuropsychology, found that the mental deterioration was no better in younger adults with diabetes than in an older group, suggesting that the damage is done early in the disease and remains stable thereafter.

“Speed and executive functioning are thought to be among the major components of cognitive health,” said Roger Dixon, the report’s co-author. “The good news is that, at this point, the cognitive slowing would not be notable in most older diabetes patients’ everyday life activities. It may be noticed, however, if the patient is involved in technical psychomotor tasks (such as video games) requiring quick and accurate responses or monitoring. The bad news is that this slowing may indicate the ‘leading edge’ of progressive cognitive decline occurring with diabetes, and it will likely get worse without careful disease management.”

Professor Dixon says that people with serious cases of type 2 diabetes should be screened for these cognitive effects to make sure they get the right medication and advice on diet or mental training. “There could be some ways to compensate for these declines, at least early and with proper management,” he said.

With diabetes a risk factor for neurode-generative diseases such as Alzheimer’s, the researchers are calling for further study to discover whether the relatively mild early effects can be linked to more serious cognitive degeneration later on.

Obesity is one of the principal causes of type 2 diabetes, and has contributed to a rapid rise in the numbers of people with the condition. As concern about Britain’s obesity problem rises, on Saturday the Government began a television and billboard advertising campaign, Change4 Life, to “kickstart a lifestyle revolution for every family in order to halt the rising tide of obesity”.

About a quarter of English adults are obese, and one official forecast suggests nine out of ten adults will be overweight or obese by 2050.

Diabetes is linked to heart disease, stroke, amputations, kidney failure and blindness, and about one in ten deaths is linked to the disease. This is forecast to rise to one in eight next year.

The Alberta study used 41 adults with diabetes and 424 without, aged 53 to 90.

Previous studies have suggested that diabetes may impede cognition, but the Alberta study is the first to identify which elements of brain function are affected and to show that the effects appear early in the progress of the disease.

Increasing peril

2.5 million in Britain have diabetes; 90 per cent have type 2

Last year there was a 7 per cent rise in diabetics, twice that of the previous year

Some estimates suggest four million people in Britain will be diabetic by 2025

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