John Gallacher is Professor of Cognitive Health at Oxford University and Director of Dementias Platform UK (DPUK), a MRC-funded public-private partnership focused on accelerating research into the early detection and treatment of dementia. With a new diagnosis every three seconds and more than 50 million cases globally, dementia is one of the biggest public health challenges facing science and governments in the 21st century. An expert on brain health and the use of big data in medical research, Professor Gallacher holds a visiting professorship at Imperial College London and an honorary professorship at the University of Hong Kong. He is the Principal Investigator for the Caerphilly Prospective Study (CaPS) and a member of the UK Biobank Strategic Oversight Committee.