The 65+ Dementia Study aims to determine whether there is unrecognised prion disease in the older Lothian population. Around 100 people in the UK are diagnosed with prion disease every year, however we think that more might be infected but their illness may not have been recognised, perhaps because the signs and symptoms are similar to different forms of dementia. This research will use patient assessment, blood samples, brain scans and samples of brain tissue from people in Lothian when they die, to find if prion disease is being missed and why.