Acoustic stimulation during sleep predicts long‐lasting increases in memory performance and beneficial amyloid response in older adults

Background Phase‐locked acoustic stimulation (PLAS) during slow wave sleep (SWS) is able to boost SWS and – as a downstream effect – improve sleep‐dependent memory consolidation. Due to an assumed bi‐directional link between SWS disturbances and memory decline in aging, older adults might benefit most from interventions targeting SWS improvements. Method Here, 32 healthy older adults (mean age: 68.9) were allocated to an intervention or control group and completed a three‐night protocol with either real‐PLAS (intervention group) or sham‐PLAS (control group), preceded by a baseline night with sham‐PLAS and an adaptation night. Memory was assessed across the intervention and at a one‐week and three‐months follow up. Result PLAS consistently induced an entrainment of slow oscillations (SOs) with stimulation‐locked increases in spectral‐power bands associated with sleep (SO, delta, and spindle power) as well as a global increase of 24% in the number of SO‐coupled spindles, a proposed mechanism for memory consolidation. The individual magnitude of the PLAS‐induced increases in spectral‐power bands and SO/spindle coupling strength predicted memory performance across the intervention and up to three months post intervention in a dose‐dependent manner. PLAS‐induced increases in memory performance were further associated with a direct beneficial change in plasma amyloid levels. Importantly, all results were exclusive to the intervention group. Conclusion We demonstrate for the first time that PLAS is associated with both long‐lasting benefits in memory and metabolite clearance in older adults, rendering PLAS a promising tool for the treatment of cognitive decline.