The promise of portable remote auditory stimulation tools to enhance slow-wave sleep and prevent cognitive decline

Dementia is the seventh leading cause of mortality, and a major source of disability and dependency in older individuals globally. Cognitive decline (and, to a lesser extent, normal ageing) are associated with sleep fragmentation and loss of slow-wave sleep. Evidence suggests a bidirectional causal link between these losses. Phase-locked auditory stimulation has emerged as a promising non-invasive tool to enhance slow-wave sleep, potentially ameliorating cognitive decline. In laboratory settings, auditory stimulation is usually supervised by trained experts. Different algorithms (simple amplitude thresholds, topographic correlation, sine-wave fitting, phase-locked loop, and phase vocoder) are used to precisely target auditory stimulation to a desired phase of the slow wave. While all algorithms work well in younger adults, the altered sleep physiology of older adults and particularly those with neurodegenerative disorders requires a tailored approach that can adapt to older adults' fragmented sleep and reduced amplitudes of slow waves. Moreover, older adults might require a continuous intervention that is not feasible in laboratory settings. Recently, several auditory stimulation-capable portable devices ('Dreem (R)', 'SmartSleep (R)' and 'SleepLoop (R)') have been developed. We discuss these three devices regarding their potential as tools for science, and as clinical remote-intervention tools to combat cognitive decline. Currently, SleepLoop (R) shows the most promise for scientific research in older adults due to high transparency and customizability but is not commercially available. Studies evaluating down-stream effects on cognitive abilities, especially in patient populations, are required before a portable auditory stimulation device can be recommended as a clinical preventative remote-intervention tool.

Automated summary

Dementia is a major cause of death and disability in older individuals, and is associated with sleep fragmentation and loss of slow-wave sleep. Auditory stimulation has shown promise in enhancing sleep quality and potentially ameliorating cognitive decline. However, tailored approaches for older adults and further studies on the downstream effects are still needed before recommending portable auditory stimulation devices as clinical intervention tools.