Blood cholesterol and risk of dementia in more than 1·8 million people over two decades: a retrospective cohort study oleh Masao Iwagami, MD, Nawab Qizilbash, MRCP, John Gregson, PhD, Ian Douglas, ProfPhD, Michelle Johnson, MSc, Neil Pearce, ProfPhD, Stephen Evans, ProfMSc, Stuart Pocock, ProfPhD