An expanding waistline and other middle-age vices are not only bad for your heart – they could cause your brain to shrink, warn researchers.
Smoking, diabetes and high blood pressure also take their toll on the grey matter, having an effect on brainpower just ten years later.
Researchers said doctors could use the information to pick out patients at a higher risk of dementia and encourage them to improve their lifestyles while there was still time.
More than 1,300 men and women in their 50s and 60s had their weight and height measured at the start of the U.S. study and had blood pressure, cholesterol and diabetes tests.
Scans to measure brain volume were carried out over the next ten years and mental tests were also run on participants.
The brain shrinks with age, even in the healthiest of people. But in those with diabetes, the hippocampus, the brain’s ‘memory hub’, shrank more quickly than in those without the condition.
The hippocampus also shrivelled faster in smokers. And those with high blood pressure were more prone to small lesions or areas of brain damage, known as ‘white matter hyper-intensities’.
High blood pressure was also linked to a more rapid worsening of scores on mental tests, effectively ageing the brain by up to eight years.
Those who were obese in their 50s tended to fare poorly on the mental tests in the study at the University of California at Davis, the journal Neurology reports.
Study author Charles DeCarli said: ‘Identifying these risk factors early could be useful in screening people for dementia and encouraging people to make changes to their lifestyle before it’s too late.’
A previous study of American pensioners found that obesity ages the brain by up to 16 years. It is thought that high levels of fat raise the odds of the arteries clogging up, cutting the flow of blood and oxygen.
People who are overweight at 60 are more than twice as likely to get dementia by 75.