Transport noise is a major problem in Europe. Over 100 million people are living in areas where road traffic noise exceeds levels greater than 55dB, the health-based threshold set by the EU.

And its not just bothering your ears. A new study by the University of Oxford and the University of Leicester has found a connection between traffic noise and obesity. Long-term exposure to road traffic noise, such as living near a motorway or on a busy road, was associated with an increase in body mass index and waist circumference, which are key markers of obesity. The study was published today in the journalEnvironmental Research.

While modest, the data revealed an association between those living in high traffic-noise areas and obesity, at around a 2% increase in obesity prevalence for every 10dB of added noise, says lead author Dr. Samuel Yutong Cai, a senior epidemiologist at the University of Oxford. The association persisted even when we accounted for a wide range of lifestyle factors, such as smoking, alcohol use, physical activity, and diet, as well as when taking into account the socio-economic status of both individuals and the overall area. Air pollution was also accounted for, especially those related to traffic.

Oxford University says this is the largest study to date on noise and obesity, looking at data on over 500,000 people from three European biobanks in the UK, Norway, and the Netherlands. Links between noise and weight were found in the UK and Norway, but not the Netherlands cohort. The researchers do not give any real cause for this difference, but they suspect that the Dutch research group (12% of the total) has a different balance between urban and rural participants. Possible reasons include that rural residents may have to rely more on cars on daily living and hence be less physically active. Another possible contributing factor is that exposure misclassification of road traffic noise in rural or intermediate areas may be lesser as compared to urban areas, where geography is much more complex.

While the study is unable to confirm a causal relationship, the results echo those from a number of previous studies conducted in other European countries.It is well-known that unwanted noise can affect the quality of life and disturb sleep, says co-author Professor Anna Hansell, Director ofthe University of Leicesters Centre for Environmental Health and Sustainability. Recent studies have raised concerns that it also may influence general health, with some studies suggesting links to heart attacks and diabetes. Road traffic noise may increase stress levels, which can result in putting on weight, especially around the waist.

On the individual level, sticking to a healthy lifestyle remains a top strategy to prevent obesity, says Dr. Cai. However, at the population level, these results could have some policy implications. Environmental policies that target reducing traffic noise exposure may help tackle many health problems, including obesity.

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Long-term exposure to traffic noise may impact weight gain, Oxford study says. But not in the Netherlands - Innovation Origins