Interview with study director Dr. Uwe Müller: “The heart needs to rest at night”
Dr. Uwe Müller from the German Aerospace Centre (DLR) in Cologne directed the NORAH Sleep Study. In an interview the physicist talks about whether the results surprised him, and about how he slept himself during the research project.
Dr. Müller, what do people need in order to sleep well?
A dark and quiet environment is very important. They should be able to lie comfortably and switch off from the worries of the day. It also helps to go to bed at roughly the same time every night and with the same routine. We also know from research that the light in the evening should be quite dim so that the sleep hormone melatonin can be released.
Apropos “the worries of the day”: worries also play a role in NORAH. People who had a more negative attitude towards air traffic were less likely to sleep well. Do you have any explanation for this?
No, that’s like the chicken and the egg. The study design of NORAH does not allow us to determine what was there first. Nonetheless, there is a clear connection: people who objectively sleep less well generally have a more negative attitude towards aviation noise or the airport.
The NORAH participants slept better than the study participants ten years previously in the Cologne/Bonn area. But they still felt more annoyed by aviation noise. How can this be reconciled?
Our results here correlate with those of the NORAH Quality of Life Study. There it was also shown that people felt more annoyed today by aviation noise than they did several years ago. The annoyance depends only to a certain extent on the actual noise exposure. There are also non-acoustic factors that play a role – lack of confidence in the authorities, for example, or in the information provided by the airport, could have an influence. We do not know whether this was the case here. I regard it as plausible, however, that the responses of the Quality of Life Study also apply to our participants.
Which results surprised you in particular?
I was looking forward to seeing whether the wake-up probability in Frankfurt after the introduction of the night flight curfew would differ from the results of the Cologne/Bonn study. In Cologne/Bonn there was continuous night flight operation at the time. There are some moderate differences, which, however, due to the different study conditions, have to be interpreted with great care. For me the result is a further indication that the aviation noise laws for determination of the nocturnal abatement zones in Germany has to finally move away from purely physical and acoustic values towards physiological values such as, for example, the wake-up reaction. And I was delighted that the “vegetative- motor” method worked so well. Although it does not measure the wake-up reactions, it is possible to determine when the heartbeat is accelerated due to aviation noise even if the person does not wake up. The method is therefore more sensitive than the sole consideration of the wake-up reaction. We may have even found one of several possible further explanations of how nocturnal aviation noise could increase the risk of cardiovascular disease. Whether this is actually the case will have to be the subject of future studies.
What might this connection look like?
The “vegetative-motor” method measures heart frequency accelerations and body movements. The heart needs to rest at night. We have found out, however, that overflights interrupt this rest and accelerate the heartbeat. This could lead to cardiovascular problems after long years of noise exposure.
How well did you actually sleep yourself during the NORAH Study?
It was quite mixed! For example, the stress was high in the summers of 2011 and 2012; that also had an effect on my sleep. I was on site at the time to recruit study participants and carry out preliminary investigations. I think it is very important to be on site personally. Sitting at a desk studying noise charts is completely different to experiencing the noise for yourself. At this point I would also express my sincere thanks to all the participants in the sleep study for their interest, their patience and endurance and their time. And thank you also to the project workers and students at the University of Gießen, who gave us decisive support by taking care of the study participants on site in the evenings and in the mornings, as well as the colleagues at the University of Pennsylvania for their valuable and intensive collaboration in the development of the new method.
Dr. Müller, thank you for talking to us!