Researchers at the Helmholtz Munich and the Ludwig-Maximilians-University (LMU) Munich have investigated a possible association between exposure to road traffic noise and the risk of metabolic diseases. Therefore, they used imaging data from MRI examinations of over 11,000 German National Cohort (NAKO) participants and combined this with road traffic noise data from Germany. Their findings indicated that exposure to road traffic noise was associated with higher volumes of adipose tissue in the body, which could also increase the risk of associated diseases.
According to the World Health Organisation (WHO), noise pollution is the second most harmful environmental risk factor after air pollution. From 53 decibels (dB(A)), noise is classified as proven to be harmful to health ‘The aim of our study was to investigate the association between road traffic noise pollution at the place of residence and the extent of fat depots under the skin and around the organs and in the liver,’ reports Fiona Niedermayer, NAKO scientist at the Helmholtz Munich.
For the analyses, the researchers used imaging data from 11,101 NAKO participants taken between 2014 and 2016 as part of the baseline MRI examination. An AI-supported approach was used to determine and measure the fat tissue volume on the MRI images. Participants with very high hepatic fat content in combination with excessive alcohol consumption or a known hepatitis B or C diagnosis were excluded from the analysis. The MRI data was correlated with information from the European Environment Information and Observation Network (EIONET) on noise pollution from road traffic in Germany for the reference year 2017. In addition to the measured noise exposure and the self-assessment by participants, the analyses also took into account other factors such as the age of the participants, individual and regional socio-economic status, self-reported pre-existing conditions, lifestyle factors, and environmental factors, including air pollution or residential greenness.
In their analysis, the scientists observed that an increase in road traffic noise of 10 dB(A) was associated with higher volumes of adipose tissue and higher hepatic fat content in men and women. ‘We were also able to observe this correlation for some out comes where the measured residential noise exposure was below 53dB(A) overall, i.e. in the actually still harmless range,’ adds Fiona Niedermayer. ‘The noise associations remained consistent even after including additional factors such as air pollutants and residential greenness as well as age, socio-economic status, pre-existing diseases and lifestyle in the analysis. This indicates that there is an independent relationship between exposure to road traffic noise and the fat depots we analysed.’
Increased adipose tissue depots and hepatic fat content are early risk factors for the development of cardiometabolic diseases such as stroke or high blood pressure. ‘An increase in adipose tissue depots and hepatic fat content shows that noise initiates metabolic processes that increase the risk of type 2 diabetes and cardiovascular disease,’ reports Professor Dr Annette Peters, Director of the Institute of Epidemiology at the Helmholtz Munich. ‘Previous studies have shown that night-time noise exposure affects the quality of sleep. This can influence stress and hormonal balance, which can impact body weight and fat distribution. Therefore, not only behavioural but also non-behavioural risk factors should be investigated in the prevention of obesity and secondary diseases by reducing traffic noise.’
The researchers point out that the traffic noise data for Germany was and is not collected nationwide. The traffic noise data for 2017 was used for the current analysis and therefore does not cover the entire study period of the participants. Consequently, participants for whom no EIONET data was available at their place of residence could only be included in the analysis if a low noise exposure limit of 40 dB(A) was used. This may have led to an underestimation of the associations. The scientists recommend that future research on noise pollution in Germany should include comprehensive and continuous assessments of traffic noise in Germany, as well as other sources of noise, and the definition of maximum exposure limits similar to those for air pollutants.