Ageing-related pathologies of the brain

There are many common structural changes that develop in the brain over the human lifespan.^6,16,84,124 These changes are heterogeneous, complex and come with a great deal of inter-individual variability. There are innumerable stress-ors, both intrinsic and extrinsic, that are associated with such changes that are thus potentially capable of accelerating and delaying the ageing process. Critically, whether these stressors and resultant age-related changes result in functional impairment is influenced by resistance, resilience and reserve.¹²¹ Given this complexity, age can be measured in different ways. Chronological age refers to the duration of time an individual has lived. In contrast, biological age is a measure based on a biomarker (e.g. epigenetic alterations and DNA methylation) that reflects functional decline and the presence of decay or disease.