What is the link between microbiota and sleep? Is this connection already important in the first days of life?
Increasingly, research with adults and animal studies reveals that sleep patterns and sleep quality show links to gut bacteria. In our new study, those children with “more immature” sleep also had more “immature” gut microbiota. These measurements were taken with healthy infants at 3, 6, and 12 months of age. The results show, for example, that a less diverse intestinal flora is associated with proportionally more sleep during the day. More daytime sleep at this age means a generally more “immature” sleep pattern, because daytime sleeps decrease as a gradual process with age. Similarly, a less diverse intestinal flora at this age means a more immature pattern, because the diversity of intestinal bacteria develops rapidly, especially in the first three years of life.
What are gut bacteria, where do they come from and why are they important?
Bacteria are the little helpers on and in our bodies, most of them inhabiting the gastrointestinal tract. Their primary task is to help digest food to make energy available to the body. About as many bacterial cells inhabit us as we have own endogenous human cells. The gut bacteria ecosystem is very complex and dynamic. Its development takes place in the first 3 years of life, only then is it comparable to the bacterial diversity of adults. Intestinal bacteria are in communication with the brain, they produce important neurotransmitters, e.g. serotonin – a messenger substance that is not only found in the brain but also in the periphery. Intestinal bacteria are important for health and change during illnesses, for example they are altered in connection with anxiety disorders or depression, but also with gastrointestinal diseases, e.g. irritable bowel syndrome. Their structure is determined by our way of life, by diet, antibiotics, lifestyle, as well as by the direct environment (e.g. who shares the household). Recently, it has been recognised that gut bacteria also change with the rhythm of the day and are influenced by the sleep-wake rhythm.
How do I ensure a good microbiome for my baby (and perhaps calm and restful nights for the parents)? Shouldn’t parents be better informed?
Unfortunately, no concrete recommendations can yet be derived directly from the current state of knowledge. However, there are indications that a regular daily rhythm can help babies find their sleep-wake rhythm. In addition to bedtimes, this also includes a regular eating schedule.
We do our best every day to bring the findings to the media and social media, have a trilingual BLOG and regularly participate in public discussion forums. We strive to make explanatory videos to make news in short form more visually tangible for society and other researchers.
What are your latest findings? And how are these findings useful?
The sleep-gut-brain connection already exists in the first year of life and is particularly strong at about 3 months of age. The maturation of sleep regulation is linked to the maturation of the gut microbiome and both are linked to behavioural development. We have studied this with the help of 160 families and babies, which is a huge effort of 6 years of research so far. We are working with experts in microbiology and gastroenterology to create a sound overall picture.
We are laying the foundations for the question of how the sleep rhythm develops. The extreme case of chronically insufficient sleep in the phase of development has been investigated in animal studies and showed as a consequence later changes in behavior and brain structure. The growth phase is uniquely sensitive, with intestinal bacteria also being relevant for healthy development. Chronic malnutrition affects gut bacteria in animals and shows similar consequences as chronic lack of sleep. It is therefore important to create standard norm data in order to identify which specific early factors have a significant impact on development. This allows us to transfer when there are problems and to address the supporting factors regarding sleep and nutrition individually.
Your research involves a strong bond with families. Has the health crisis complicated your research activities?
The pandemic has been a huge challenge for our work, as we depend on the help of society and families in particular. Many families participate in our studies for a long time and take part in our measurements several times during the course of the children’s development. In the meantime, we have conducted online surveys where we examined changes of children’s sleep due to the confinement. We were very pleased that many families also participated online, which gave us new insights into sleep during the pandemic.
What is the most important finding from the pandemic studies? Is there anything surprising about the results?
The pandemic is/was an exceptional health situation that also affected the sleep of infants and young children. Our results show negative secondary consequences of the lockdown in various areas of the sleep quality of babies and young children. But the results also show that we have the possibility to influence the consequences ourselves in order to improve the situation, for example by reducing stress and practising mindfulness techniques.
First, studies with adults showed an increase in sleep duration at the beginning of the lockdown, whereas the babies in our study experienced a continuous shortening of sleep. Second, within a few months, sleep quality returned to the same level as estimated before the pandemic. Third, the more time the parents spent with the children, the shorter the estimated time to fall asleep and the less interrupted the sleep was – which means better sleep quality for the children.
How did children’s sleep change during the lockdown?
We evaluated the parents’ assessment in April 2020 in two age-specific groups. An acute deterioration in sleep quality was evident in both groups. Babies had on average 8 minutes longer bedtimes, 22 minutes later bedtimes and 7 minutes shorter sleep. A similar pattern was observed in preschool children, with less regular bedtimes, increased longer bedtimes, more irregular sleep duration and increased waking. The long-term observations in May and June 2020 showed different patterns. Babies’ bedtimes had already returned to normal after 1 month, but sleep duration remained somewhat shortened. Bedtime and waking time remained unchanged. In preschool age, bedtimes became more regular again in the long-term course and the time to fall asleep became shorter again, but the regularity of sleep duration and waking remained unchanged.
Which children were particularly affected by the lockdown?
Research colleagues in Israel showed that 35% of mothers observed a shortened sleep duration of their babies. In addition, the occurrence of maternal anxiety was related to a shorter sleep duration of the children. Our results show that babies experienced a constant reduction in nighttime sleep duration of 29 minutes in total. This deserves attention because, in general, there is an increase in nighttime sleep duration until about 3 years of age. This age includes important developmental and learning phases in which the brain changes and needs the rest during sleep for these neuronal processes to occur.
Are there long-term consequences of the changed sleep the lockdown created?
Normalisation in the course of the restrictions took place only partially, for example not in the length of time the babies slept at night. It was necessary to find a way to get used to the new rhythm and to reorganise within the families due to the restrictions. Depending on the individual situation, this was more or less possible.
We have the possibility to learn to cope with very challenging situations. For this we need information with a scientific basis and the knowledge of which methods are effectively protective. Very important is the public and transparent dissemination of this information to society, with unrestricted access for everyone. In addition, those who are particularly at risk should receive professional support.
What insights do you hope to gain next?
With the support of many master’s and bachelor’s students, several members of our team are working on various specified topics related to sleep, e.g. the role of nutrition, how to support children with regulation disorders, the role of rhythm in pregnancy, etc. We are also working on the identification of protective factors in order to pass these on as concrete recommendations to society. In addition, we continue to analyse data on the consequences of the pandemic in order to identify protective factors and to be able to pass these on to society as concrete recommendations.