esanum: Dr Stefani, your presentation at this year's EAN (European Academy of Neurology) Congress is entitled “Six million years of evolution. Do we fit into today's society?” To put it bluntly: have we adapted well enough to mobile phones and other modern technology?
Dr. Ambra Stefani: I don't think we have adapted optimally yet. Although we have some means of adaptation, terms such as ‘social jet lag’ clearly show that we have a problem adapting to modern society. Social jet lag describes the discrepancy between our biological rhythm and the social rhythm. This already affects a large part of the population. Although there is little epidemiological data available, according to data from Brazil, up to 70 percent of the total population probably suffers from it, with clinically relevant cases accounting for around 13 percent. Social timekeepers, such as working hours, school start times or early meetings, as well as long commutes, mean that people who prefer to go to bed late in particular find it difficult to fall asleep early. This results in chronic jet lag and, in the long term, sleep deprivation.
esanum: Your research focuses on sleep medicine. What connections are known or are the focus of research in the this field? What do sleep patterns have to do with the ability to adapt?
Dr. Ambra Stefani: In the sleep laboratory, we see patients who develop symptoms due to ‘social jet lag’ and chronic sleep deprivation. It is well known that social jet lag has far-reaching consequences. It is associated with an increased risk of various neurological diseases and psychiatric disorders such as depression, and can also increase the risk of cardiovascular and metabolic diseases such as diabetes. This failure to adapt to social time cues thus has far-reaching effects on our entire organism.
esanum: How do you classify chronotypes and how do they rank in terms of adaptability?
Dr. Ambra Stefani: Most people belong to a normal chronotype. Extreme early or evening types are rather rare. Nevertheless, even people with a moderate preference for late bedtimes can suffer from socially fixed working or school hours, especially over longer periods of time.
The lecture [at the EAN] also dealt with how chronotypes have evolved. In earlier societies, which lived more closely with nature and slept in groups, often outdoors with fire for protection, it was advantageous to have someone awake at all times. This was not a matter of being forced to stay awake, but rather a natural distribution of waking phases. Studies of recent indigenous peoples in Africa or South America show that at least one group member is awake for over 99 percent of the night. The reason for this is the different chronotypes within the group: some sleep earlier and wake up earlier, others vice versa. This probably offered a survival advantage for the group and was selected for evolutionarily. Therefore, there are probably also different chronotypes in our society today.
esanum: Are there any advantages or disadvantages in terms of performance for early risers or night owls?
Dr. Ambra Stefani: In our current post-industrial society, early risers have an advantage, as punctuality and early working hours are often considered more productive. Biologically speaking, however, there is no inherent advantage of one chronotype over another. From a biological perspective, everything indicates that a diversity of chronotypes was beneficial to society, at least in the past.
esanum: Another very important area of research is the link between sleep disorders and the risk of dementia. Are there any new findings in this area?
Dr. Ambra Stefani: There is a growing body of data showing that sleep disorders or changes in sleep can increase the risk of dementia. In particular, extremely short sleep times (less than six hours) but also excessively long sleep times (more than nine hours) are associated with an increased risk of dementia, as are sleep fragmentation and chronic sleep deprivation.
We conducted retrospective studies on a large cohort of patients in Innsbruck and – in line with the findings of other research groups – found that patients with low levels of deep sleep and REM sleep and an increased proportion of light sleep and wakefulness during the night have an increased risk of developing dementia later in life. These sleep changes were already visible in our study at least five years before the development of dementia, and we followed patients for an average of up to twelve years. These are therefore very early changes.
esanum: And what follows from this?
Dr. Ambra Stefani: It means that we can identify these risks early on and take preventive action. The international recommendation is to sleep seven to nine hours a day and maintain a regular sleep-wake cycle, i.e. go to bed and get up at roughly the same time every day. Catching up on sleep at the weekend may help in the short term, but it does not reduce the risk of other diseases in the long term.
The hope is that we will be able to improve our sleep in the future with the help of new technologies. Studies are currently investigating how acoustic stimulation can increase the proportion of deep sleep. This is still in the research phase, but there is hope that in the future we will be able to improve not only the duration but also the quality of our sleep using various tools.
In addition to the risk of dementia and neurodegeneration, I would like to mention the so-called glymphatic system. This is a relatively new concept: it is a waste disposal system in our brain. When we are active – and our brain is always active, even when we are asleep – waste products are generated. Certain proteins can cause problems if they remain in the brain and accumulate.
The glymphatic system is responsible for disposing of these products and is much more active during sleep, especially deep sleep, than when we are awake. This is probably a mechanism that can reduce the risk of dementia and other neurodegenerative diseases through good sleep.
esanum: Another interesting topic is dementia subtypes. Which ones are particularly relevant to our modern, digital age?
Dr. Ambra Stefani: It is difficult to relate this directly to our current society. The glymphatic system seems to be more relevant for Alzheimer's dementia than for other diseases, but it probably plays a role in all neurodegenerative diseases. In Parkinson's disease, another sleep disorder is often present many years earlier: REM sleep behaviour disorder, in which patients can move around and act out their dreams during REM sleep. We know that these patients have a very high risk of developing Parkinson's disease after 15 years.
Of course, there are several factors at play here. As I said, it is difficult to relate this directly to our current society. But screen exposure, even in the evening hours, generally affects our sleep. During the day, we are often indoors – at work or at school – and our exposure to natural sunlight is therefore reduced. In the evening, on the other hand, we are exposed to far too much light, even though our bodies do not need it. This also leads to disturbed sleep. Current technology could help here, for example by simulating sunlight exposure indoors.
esanum: That suggests that we should also engage in a bit of digital detoxing.
Dr. Ambra Stefani: Yes, although it must be said that technology can also be helpful. Take simulated sunlight exposure, for example: there are lamps whose light intensity changes throughout the day to simulate natural sunlight. Temperature is also very important for sleep. There are mattresses that allow you to set a comfortable temperature, which then adjusts to your body temperature throughout the night. And as already mentioned, there are also mechanisms for specifically promoting deep sleep, although these are still in the research phase. So technology can help us improve our sleep. However, we must be careful: exposure to light in the evening, especially blue light from screens, disrupts our melatonin production. Melatonin, a sleep hormone, is produced by our body, especially when the light decreases. However, if we constantly look at screens, this physiological process does not function optimally.
esanum: What follows from the fact that we should pay attention to our sleep?
Dr. Ambra Stefani: Yes, exactly. This is an important point, because many people think that good sleep is desirable, but rather secondary. However, I believe that more and more people are becoming aware of the far-reaching consequences of sleep for neurological, psychiatric and general cardiovascular diseases. Many people are now paying more attention to their exercise and nutrition, and sleep should also be given more attention.
Dr Ambra Stefani is senior physician and deputy head of the Centre for Sleep Medicine (Zentrums für Schlafmedizin) at the University Clinic for Neurology at the Medical University of Innsbruck, completed her PhD in clinical neuroscience and her specialist training at the University Clinic for Neurology at the Medical University of Innsbruck, Austria (Medizinischen Universität Innsbruck). Her research focuses on sleep medicine, the relationship between sleep and neurodegeneration, REM sleep behaviour disorder and restless legs syndrome.