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INTRODUCTION: It remains unclear why age increases risk of Alzheimer’s disease and why some people experience age-related cognitive decline in the absence of dementia. Here we test the hypothesis that resilience to molecular changes in synapses contribute to healthy cognitive ageing. METHODS: We examined post-mortem brain from people in mid-life (n=15), healthy ageing with either maintained cognition (n=8) or lifetime cognitive decline (n=7), and Alzheimer’s disease (n=13). Synapses were examined with high resolution imaging, proteomics, and RNA sequencing. Stem cell-derived neurons were challenged with Alzheimer’s brain homogenate. RESULTS: Synaptic pathology increased, and expression of genes involved in synaptic signalling decreased between mid-life, healthy ageing and Alzheimer’s. In contrast, brain tissue and neurons from people with maintained cognition during ageing exhibited decreases in synaptic signalling genes compared to people with cognitive decline. DISCUSSION: Efficient synaptic networks without pathological protein accumulation may contribute to maintained cognition during ageing.