Figure 1.

Study design. This study consisted of five over-night-, and two 1-hour follow-up visits (1-week and 3-months post-intervention) to the sleep laboratory at the University Psychiatric Hospital in Bern. The first visit was an adaptation and screening night (Adapt) to exclude sleep pathologies. Participants spent the subsequent night in their own home and returned to the lab for four consecutive nights. Next, a baseline night (Baseline) assessed participants’ sleep using sham-PLAS, where the PLAS algorithm marked detected SO peaks, but no stimulation ensued. Finally, three experimental nights contained real-PLAS for the intervention group or sham-PLAS for the control group. Participants completed a face-occupation association (FOA) memory task eight times across the intervention, including the two follow-ups (t0–t7). Initial encoding took place on the evening before the first experimental night where the associated stimuli were presented in two encoding runs (t0). As a baseline, this session also contained an immediate cued recall run, where the faces were shown and participants verbally responded with the corresponding occupations. The remaining sessions (t1–t7) comprised cued recall and were assessed at all mornings (mor), evenings (eve) and follow-ups, with faces presented in random order. From t1 to t4, recall trials contained written feedback showing the correct response as additional learning runs. In the morning after the baseline night (pre-intervention) and after the last experimental night (post-intervention), participants completed additional cognitive assessments and blood samples were taken to be analysed for plasma Aβ. Cognitive assessments were repeated at the two follow-ups. Please refer to the SI, Section 2 for detailed descriptions of the FOA task, all additional cognitive and sleep-related assessments as well as stimulus material.