Some forms of dementia may not be confined to the central nervous system; they may not even begin in the brain. A systematic review of more than 200 studies has now found that as many as a third of all dementia cases are tied to diseases outside the brain. That's nearly 19 million dementia cases globally. The findings join growing evidence that suggests there are many distinct subtypes of dementia and not all of them necessarily originate in the brain. There's a chance that some peripheral