John Snowdon is Clinical Professor at the Discipline of Psychiatry, Sydney Medical School, and Old Age Psychiatrist for Sydney Local Health District, Sydney, Australia. Graeme Halliday is Senior Specialist in Psychiatry, Sydney Local Health District, Sydney, Australia. Sube Banerjee is Professor of Mental Health and Ageing, Section of Mental Health and Ageing, Health Service and Population Research Department, The Institute of Psychiatry, King's College London, UK.