Polymorphisms in the Apolipoprotein E (APOE) gene have been associated with individual differences in cognition, brain structure and brain function. For example, the ε4 allele has been associated with cognitive and brain impairment in old age and increased risk of dementia, while the ε2 allele has been claimed to be neuroprotective. According to the “antagonistic pleiotropy” hypothesis, these polymorphisms have different effects across the lifespan, with ε4 for example postulated to confer benefits on cognitive and brain functions earlier in life. Using the rich cognitive and brain measures in the CamCAN cohort (www.cam-can.org), we will investigate the “antagonistic pleiotropy” hypothesis by testing for allele-by-age interactions in approximately 600 people from across the adult lifespan (18-88 years), on six outcome variables related to cognition, brain structure and brain function (fluid intelligence, verbal memory, hippocampal gray matter volume, mean diffusion within white matter, and resting-state connectivity measured by both functional magnetic resonance imaging and magnetoencephalography).