Traffic noise could increase risk of fat around midriff, says Swedish study

A pot belly might not simply be the product of too much food and not enough exercise, according to a Swedish study that found it could be related to traffic noise.
Research published in the Occupational & Environmental Medicine journal has revealed a link between exposure to road traffic, rail and aircraft noise and the risk of developing midriff bulge, one of the most harmful types of fat deposit around the body.
The results are based on 5,075 people living in five suburban and rural areas around Stockholm and their exposure to traffic noise since 1999. Researchers also used official figures on road and rail traffic noise levels and flow, as well as national data on aircraft noise from Arlanda airport.
All the participants in the study had been part of the Stockholm Diabetes Prevention Programme, which aimed to look at risk factors for the development of the disease and ways to avoid it.
Participants completed a detailed questionnaire covering lifestyle, state of health, levels of psychological distress, insomnia and job strain. They were also asked about environmental noise pollution from road traffic, trains and aeroplanes.
They underwent a medical exam, which included blood pressure and a test for diabetes, as well as measures of central body fat (the waist and hips), a waist-hip ratio and overall obesity (which is calculated using weight and height to define the body mass index).
 Researchers found that 62% of participants 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; 1108 had been exposed to aircraft noise of more than 45 dB. In all, 54% had been exposed to one source of traffic noise, 15% to two sources, and 2% to all three.

Researchers found exposure to any of the three sources of noise resulted in a larger waist size. There was a 0.21 cm increase in waist size for every additional 5 dB increase in exposure to road traffic noise – most notably among women. And there was a change of 0.16 in waist-hip ratio for every 5 dB increase in noise exposure to road traffic – an association that was stronger in men.
The more sources of noise pollution a person was exposed to at the same time, the greater the risk of a larger waist. For those exposed to all three sources, the risk of a larger waist doubled from the 25% heightened risk among people exposed to only one noise source.
Researchers did not draw any definitive conclusions about cause and effect, but said noise exposure might be an important physiological stressor and could bump up the production of the hormone cortisol, high levels of which are thought to have a role in depositing fat around the middle of the body.

“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 wrote.
Traffic noise might also affect a person’s metabolism, through sleep disturbance, altering appetite control and energy expenditure.