The stress suffered by people exposed to the noise of road traffic could be partially responsible for the obesity suffered by many Britons, according to new research.
Findings from a four year study of more than 5,000 people “suggest that traffic noise exposure can increase the risk of central obesity,” states a paper published in the Occupational & Environmental Medicine journal.
It warns that exposure to a combination of noise from road traffic, trains and planes may pose the greatest risk of getting a spare tyre, dubbed “central obesity” by researchers.
Researchers from Norway and Sweden looked at the levels of traffic noise endured by thousands of men and women living in Stockholm, who were measured for their body mass index (BMI), waist sizes, and waist to hip ratio. The study, which took place between 2002 and 2006, found that almost two thirds of people had been regularly exposed to road traffic noise of at least 45 decibels (dB) while one in 20 had been exposed to similar levels of noise from trains. And a further 1,108 had been exposed to aircraft noise of more than 45 dB.
The analysis indicated no link between road traffic noise and BMI. But there was an association between road traffic noise and waist size, with a 0.21 cm increase for every additional 5 dB increase from 45 dB. Waist sizes rose by 0.46cm and 0.99cm for the same increase in noise from trains and planes respectively. The increased risk of a larger waist rose from 25 per cent among those exposed to only one source to almost double for those exposed to all three sources, according to the study.
Stress, including people having their sleep disturbed at night, can interfere with the body’s metabolism. And exposure to noise can result in increased production of cortisol, which can in turn stimulate the accumulation of fat around the abdomen, according to researchers. “This may explain why the effects of noise were mainly seen for markers of central obesity, such as waist circumference and waist-hip ratio, rather than for generalised obesity, measured by BMI,” they write.
One of the researchers, Professor Göran Pershagen, from the Institute of Environmental Medicine at the Karolinska Institute, told The Independent: “Increased waist circumference (or central obesity) is an established risk factor for diabetes type 2 and a range of cardiovascular diseases. Consequently, the public health implications of our findings are potentially significant given the wide-spread and increasing exposure to traffic noise.” The findings are “absolutely” relevant to people in Britain, he added.
Another of the researchers, Charlotta Eriksson, an epidemiologist at Stockholm’s Center for Occupational and Environmental Medicine, commented: “There are still very few studies investigating the association between traffic noise and metabolic markers, such as BMI and waist circumference, and our results must therefore be interpreted with caution.” There are several “plausible” explanations showing how how noise may increase the risk of obesity, particularly in the “abdominal area as our research suggests.” She added: “In addition, abdominal obesity is an even stronger risk factor for disease occurrence than the BMI. Thus, our findings are of significant public health concern.”
Richard Elliott, research communications manager at Diabetes UK, said: "While this study adds to our understanding of the possible link between noise levels and weight gain, it is important to note that diet and physical activity remain the most important risk factors for Type 2 diabetes. Further research will be needed to confirm these results and find out why this link might occur. The best way to prevent Type 2 diabetes is by taking regular physical activity and eating a healthy balanced diet."