Scientists have attempted to put a number on how many dementia cases could be caused by insomnia each year – and their figure is similar to the population of a mid-sized US city. Researchers from several US institutions reanalyzed existing data on 5,899 people aged 65 and over. This included self-reported insomnia symptoms and "probable dementia" based on cognitive decline tests and medical diagnoses. The main takeaway was that 12.5 percent of dementia cases in older adults, which equates to