Improving Sleep to Prevent Cognitive Decline: An interview with Dr. Marc Züst

Meet Dr. Marc Züst

Group Leader & Deputy Head of Research

UPD Bern – University Psychiatric Hospital for the Elderly

University of Bern

Why is deep sleep (particularly slow-wave activity) so important for keeping the brain healthy and supporting waste clearance?

Deep sleep is when the brain switches into maintenance mode since it doesn't need to process constant input from the environment. Slow waves help increase fluid flow through brain tissue, which supports the clearance of metabolic waste products like amyloid beta. At the same time, deep sleep restores synaptic balance & energy metabolism and strengthens memory. It's essential for long-term brain health.

How do sleep spindles help the brain store memories, and what happens when these rhythms become disrupted with age?

Sleep spindles act like timing signals, coordinating communication between the hippocampus (the "librarian") and cortex (the "library"). With age, spindles often become fewer or less well-timed, which may weaken memory consolidation and partly explain why learning and recall become more fragile in older adults. The librarian can't find the books in the library anymore.

How do you think public health strategies can incorporate sleep monitoring and sleep health promotion as tools for early brain health protection and dementia prevention?

Sleep is a modifiable behavior, which makes it a potentially powerful prevention target. Public health strategies could include education on sleep hygiene and early interventions when sleep becomes fragmented. Integrating sleep metrics into broader brain-health checkups could help identify risk years before cognitive symptoms appear. However, we should always be cautious about over-screening since every test imparts a risk of a false-positive discovery.

Why do you think low-cost home EEG headbands have not yet reached widespread public adoption for sleep assessment? What could a low-cost, user-friendly wearable device potentially look like for large-scale adoption?

Many current devices are either uncomfortable, unreliable, or hard to interpret for non-experts. For widespread adoption, a wearable would need to be easy to use, comfortable enough for nightly wear, scientifically validated, and provide clear, actionable feedback rather than raw data. Ideally, it would run passively in the background and integrate seamlessly into daily life. We're far from that point. However, there are examples where it worked, like the CPAP machine. However, that is a direct intervention, and people using it will often experience an almost instant improvement in their daily life. For a preventative sleep monitoring-, or even boosting—device, you'd have to convince people to use it even though they will not see any direct benefits. Even if they then, 20 years later, have aged healthily, it's almost impossible to trace that back to the intervention. They might have aged just as healthily if they hadn't worn the device for 20 years, every night. For this reason alone I personally think these devices will never find their way into routine preventative use.

However, maybe there's a better way of achieving the same goal: Recent studies have suggested a bidirectional link between socializing and sleep quality, and both of these factors are implicated in cognitive decline as well. So if we can eliminate loneliness in old age, we might fill several needs with one deed. There are good public health initiatives already underway that aim to reduce old-age loneliness, like the "connect!" initiative

What simple changes in daily habits or sleep routines might help improve slow waves and spindles as we age? What affordable, non-invasive strategies for sleep might lower dementia risk and help slow cognitive decline?

Regular sleep schedules, sufficient daylight exposure, physical activity, and reducing evening light and alcohol can all support healthy sleep rhythms. Even small improvements in sleep continuity can benefit slow waves and spindles. See also the newsletters.