The occurrence of dementia and Alzheimer's disease may have stabilised in some wealthy nations, according to a study released Friday. A review of data from Sweden, the Netherlands, Britain and Spain showed the percentage of the population with dementia — the umbrella term for neurodegenerative diseases of the brain — holding steady, along with the number of new cases, said the study, published in The Lancet Neurology. Researchers led by Carol Brayne, a professor at the Cambridge Institute of Public Health and the University of Cambridge, compared dementia occurrence in old people across two time periods spanning the last several decades.