Skip to content
Home » Deep Impacts about Deep Sleep: Stephanie Huwiler (Transcript)

Deep Impacts about Deep Sleep: Stephanie Huwiler (Transcript)

Here is the full transcript of Stephanie Huwiler’s talk titled “Deep Impacts about Deep Sleep” at TEDxHWZ conference.

Stephanie Huwiler’s talk, “Deep Impacts about Deep Sleep,” delves into the crucial role that sleep plays in cardiovascular health, emphasizing it as a form of cardiovascular vacation essential for long-term well-being and the prevention of diseases. She discusses how her research focuses on unraveling the effects of sleep on heart health and introduces the concept of slow waves in deep sleep as pivotal for cleansing the brain and enhancing cardiovascular functions.

Huwiler explains that enhancing these slow waves through auditory stimulation during sleep could improve heart function by promoting stronger contractions and relaxation of the heart. Despite the potential benefits, she highlights challenges, such as the loss of stimulation efficiency with age and the complexity of implementing this technology outside of a lab setting.

Huwiler also offers practical advice for improving deep sleep quality, including avoiding caffeine and alcohol close to bedtime, reducing daytime naps, and engaging in regular exercise. She advocates for the prioritization of sleep as a vital component of health maintenance, likening it to a mini-vacation for the heart that deserves attention.

Huwiler concludes by emphasizing sleep’s role as a powerful recovery system, underscoring the need for further research and the development of technologies to harness its benefits for cardiovascular and overall health.

Listen to the audio version here:


Imagine that it’s late night, you lie in your bed, tucked comfortably under your blanket. And as you close your eyes and slowly drift off to sleep, your heart travels to some place far. Maybe to a tranquil beach, to relax and recover from the previous day. This may sound to you like the start of a fairy tale, but I assure you, sleep as your cardiovascular vacation is not that far-fetched after all.

Over the past few years, I found my passion and I dedicated my research to help unraveling how sleep impacts our cardiovascular health. And today, I want to share some magic ingredients of sleep that contribute to a fantastic cardiovascular vacation each and every night.

So why are these mini-vacations so important for us? Well, having a healthy heart is actually crucial in achieving healthy longevity, as cardiovascular diseases represent the leading cause of death worldwide. Even when it’s not about long-term health, improving our cardiovascular function can make a difference also in everyday life.

So recently, I’ve had the brilliant idea to prepare for my first ever half marathon. And following common knowledge, I incorporated running to increase my cardiovascular fitness. I also focused on my nutrition to fuel my body with appropriate nutrients and energy.

The Importance of Sleep for Cardiovascular Health

According to the American Heart Association, these two factors, exercise and nutrition, both belong to a list of eight key measures that help maintaining and improving our cardiovascular health. But wouldn’t it be great to also train for a half marathon while sleeping? I guess none of you dislike sleep. And personally, I fell in love with sleep.

I think sleep is absolutely amazing. And luckily, last year, getting healthy sleep was included in this list of key measures for our cardiovascular health. Meaning, finally, sleep started to get the attention it deserves. But evidence was actually out there for a while, indicating that both too short, but also too long sleep, both increased the likelihood of developing medical conditions, such as excess body fat, elevated blood pressure, or even diabetes.

These are all established risk factors for cardiovascular diseases. But this evidence, it’s also based on reducing sleep to one number only, to sleep duration. And this reflects a kind of long-held myth that sleep is a uniform process, where our brains are completely shut off and uncoupled from our bodies. A state that Edgar Allan Poe even referred to as “those little slices of death.”

Understanding Brain Activity During Sleep

But to understand whether our brains are truly silent during sleep, we have to visualize brain activity. So our brains, they’re made up of roughly 86 billion little cells, the so-called neurons. And these immense numbers, it’s comparable to the number of stars there are in our Milky Way. So think of these neurons as a big orchestra of instruments, where each instrument represents a group of neurons.

And these instruments, they can be louder and quieter, play faster and slower rhythms. And sometimes, each instrument just plays a background melody. Whereas during other times, a big group of instruments joins to play the main melody. And collectively, these instruments generate a complex musical composition that is actually consisting of brain rhythms or also brain waves.

For a century, we can measure these brain waves by attaching small sensors on the head. So this visual representation is possibly not as exciting as listening to a musical masterpiece at first, but it can tell us a lot. So you now see a 20-second brain wave trace of a person having their eyes closed. And each line represents here a different location of a sensor placed on the skull.

The Role of Slow Waves in Sleep

During this relaxed wakefulness, none of the melodies is visually extremely prominent, which is indicated by these random wiggles on these relatively flat lines. But then suddenly, during deep sleep, thousands of instruments start to play together, followed by silence, over and over again. And this results in brain waves with increased amplitude and a rhythmicity of about one wave per second. And we call these waves slow waves.

The more instruments that are joining this slow rhythmic melody, the higher the amplitude of slow waves and the deeper our sleep. And this reveals that sleep is definitely not a mere slice of death, but it’s actually a highly dynamic process. Let’s go back now to these slow waves, because I think slow waves are absolutely fantastic, because they’re true multitaskers. So they’re, for instance, involved in cleansing the brain from waste proteins that accumulate during wakefulness.

So think of slow waves as ocean waves that flush litter that has been thrown into the ocean onto the shore. And we also think that slow waves are involved in promoting our cardiovascular functions. So why is that? Actually, the older we turn, the fewer slow waves we have. This results in more fragmented and more superficial sleep with aging. And given that age is the major risk factor of cardiovascular diseases, this age-related decrease in slow waves could represent a strong link between them. But still, we do not know whether slow waves also directly cause changes in cardiovascular functions. But to do so, we have to modulate slow waves.

Advancements in Sleep Research

About a decade ago, researchers found that playing tones during deep sleep enhances these slow waves, actually without even waking people up. I mean, how amazing is that? Playing music during sleep can boost these slow waves? Well, it’s not actually music, but it’s rather bursts of noises like this. I guess you’re now all wondering how these oddly sounding noises can help to enhance deep sleep.

So let’s go back to our orchestra analogy and think of these tones that occur every second, which matches the frequency of slow waves as the conductor of our brain orchestra. And the conductor facilitates the synchrony between instruments. And again, the more instruments that are joining the slow waves, the higher their amplitude and the deeper the sleep. So we now applied the so-called auditory simulation to explore the role of these slow waves in promoting our cardiovascular vacation.

And actually, we expect that deep sleep to resemble a true relaxing at the beach vacation, which is marked by low cardiovascular activity, meaning low heart rate and low blood pressure. And generally across deep sleep, we found this level of cardiovascular relaxation. But surprisingly, when these tones were played and slow waves were enhanced, we found a cardiovascular activation, meaning a short increase in heart rate and short increase in blood pressure, but just for a few seconds. And this is kind of a dynamic response of our cardiovascular system to this enhanced slow wave.

We’re now going to term this response cardiovascular pulsations. And interestingly, these pulsations also occur naturally during very specific moments of your deep sleep. But by enhancing slow waves, we can make these pulsations occur more frequently. We think, or this experiment shows, that slow waves are truly important during sleep.

Potential Health Benefits of Enhanced Slow Waves

But are these pulsations then really beneficial for our hearts? So our hearts, they beat around 100,000 times a day. And during each cardiac cycle, the heart contracts to eject blood to the body’s arteries and relaxes again to get filled up with new blood. And after just one night of boosting slow waves, we found the hearts of our participants to contract more strongly.

But it also increased the ability of the heart to relax and get filled up with new blood. And both together, this contraction and relaxation indicate improved heart function. So this results show that one magic ingredient of sleep that promotes our nightly cardiovascular vacations are indeed slow waves. So when we fall into deep sleep, our hearts indeed travel someplace far.

But this cardiovascular vacation is possibly not just pure relaxation, but also involves some active parts. It is as if our hearts are not just exclusively sunbathing, but also serving a bit in the ocean. And these active parts, these cardiovascular pulsations, likely promote our cardiovascular function and health during sleep. So remember slow waves as ocean waves that flush litter onto the shore.

These pulsations could actually represent stronger and more frequently occurring waves that more effectively flush the litter onto the shore. And this could be even involved in processes in the brain that are actually involved in Alzheimer’s disease. So we believe that slow wave stimulation could be used in the future as a complementary method to treat cardiovascular diseases or even Alzheimer’s disease. And we also think it could be used in preventative medicines and sports to enhance cardiac function or even facilitate recovery.

Challenges and Future Directions

And maybe, if I used this technology myself, I would have run my half marathon faster if only I listened to my own research. I guess many of you are now wondering where you can download this app that plays these tones to enhance your slow waves and enhance your cardiovascular vacation.

Well, unfortunately, it’s not that simple as these tones have to be played during the right times during deep sleep to avoid sleep disruption. And simply downloading an app or even coupling it with sleep trackers such as smartwatches will not provide this necessary information.

And additionally, most studies have been conducted in sleep labs, also ours. And if you now think that participating in a sleep study is similar to spending a night in a hotel, well, this is far from reality. This was one of our participants equipped with all these sensors and cables to literally record tons of vitals. And you know, in the end, we just asked them to sleep as normally as possible.

So, we kind of transferred this specific setup directly to your homes. And unfortunately, we’re also facing some challenges such as auditory stimulation loses its efficiency with aging. It is as if our orchestra loses its ability to synchronize to an external conductor. But we are currently tackling these challenges by developing portable but also comfortable solutions with additional stimulation methods to increase slow waves and your cardiovascular vacation across the aging process.

Practical Tips for Enhancing Deep Sleep

And while we’re giving our best to develop such devices, I want to leave you with five science-backed hacks to increase deep sleep. Avoid caffeine close to bedtime as it can actually reduce time spent in deep sleep if consumed up to eight hours before going to bed. Limit alcohol consumption as it is a big myth that alcohol guarantees a good night’s sleep. It actually interferes with sleep during later parts, makes it more superficial and more fragmented.

Reduce daytime napping, especially if you have problems with your nighttime sleep. So long naps, where you even enter deep sleep, can disrupt your sleep schedule, make it harder to fall asleep, and also reduce time spent in deep sleep on the next night. And engaging in regular daytime exercise can actually greatly improve deep sleep.

But try to avoid high-intensity workouts close to bedtime as the increased rise in your body core temperature can make it harder for you to enter deep sleep. Keeping your hands and feet warm can actually facilitate this needed drop in your body core temperature to make you fall asleep more quickly. And it can also prolong time spent in deep sleep.

So I want to here highlight that sleep is a very individual process and not every method may work for everyone. But what all of us can do is to prioritize sleep in our lives as it is our body’s mini-vacation. Just as you take a vacation to relax and recharge from work, your heart also needs and deserves the vacation that deep sleep provides. So I’d like you to remember slow waves during deep sleep as your active cardiovascular vacation.

And as I’d like to say, sleep represents the most powerful recovery system that we have. Thank you.

Related Posts

Reader Disclosure: Some links on this Site are affiliate links. Which means that, if you choose to make a purchase, we may earn a small commission at no extra cost to you. We greatly appreciate your support.