People who are obese in middle age are at almost four times greater risk of developing dementias such as Alzheimer’s disease in later life than people of normal weight, according to a study released today. The study, published in the journal Neurology, examined data on more than 8,500 people over the age of 65. Of the sample, 350 had been diagnosed with Alzheimer’s disease or vascular dementia and a further 114 had possible dementia.Scientists used records of the participants’ height and weight in the decades before and found that those who had been overweight in middle age had a 1.8 times 80pc higher risk of being diagnosed with dementia in later life. But for obese people, classified as those having a body mass index BMI of 30 or above, the risk soared. People with midlife obesity had an almost four times 300pc higher risk of dementia.