Abstract
Brain deterioration and cognitive decline are considered common characteristics of ageing. However, it is clear that not everyone experiences senescence at the same rate or to the same degree. Individual differences in the quality of cognitive and brain function in old age suggest that deterioration and decay are neither ubiquitous nor inevitable characteristics of ageing. This begs the following question: what are the factors that explain some of the individual differences in old age, allowing some people to retain cognitive and brain function, while pushing others into a trajectory of decline and decay?