Over the past several decades, a worldwide demographic transition has led to an increasing number of older adults with chronic neurological conditions. These conditions, which have a profound effect on the cognitive function and physical ability of older adults, also have a long preclinical phase. This feature provides a unique opportunity to implement preventive measures for high-risk groups and the population as a whole, and therefore to reduce the burden of neurological diseases. The concept of brain health has emerged as the overarching theme to define overall brain function independently of underlying pathophysiological processes. We review the concept of brain health from the ageing and preventive care perspectives, discuss the mechanisms underpinning ageing and brain ageing, highlight the interplay of various forces resulting in deviation from brain health towards brain disease, and provide an overview of strategies to promote brain health with a life-course approach.