Nighttime aircraft noise can be fatal

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Sudden noise exposure from aircraft puts a strain on human health. Image: Unspla
Sudden noise exposure from aircraft puts a strain on human health. Image: Unsplash

Short-term disturbances caused by aircraft noise at night can lead to cardiovascular death within hours. This is shown in analyses by a team of researchers from the Swiss Tropical and Public Health Institute and Empa. The researchers used a dataset covering the years 2000 to 2015 to investigate how mortality rates in the Zurich airport area are related to acute nighttime aircraft noise exposure; they recently published their findings in the European Heart Journal.

Studies on traffic noise and cardiovascular mortality have mostly focused on long-term noise exposures. These studies indicate that chronic noise exposure is a risk factor for cardiovascular mortality. Overall, about 48,000 cases of so-called ischemic heart disease per year in Europe can be attributed to noise exposure, especially to road noise.

For the first time, a team of researchers from the Swiss Tropical and Public Health Institute (Swiss TPH) and from Empa, the Swiss Federal Laboratories for Materials Science and Technology, has now demonstrated that acute nighttime aircraft noise can cause fatal cardiovascular failure within two hours of exposure. The study, recently published in the European Heart Journal, found that the risk of cardiovascular death increases by 33 percent for nighttime noise exposure between 40 and 50 decibels and by 44 percent for exposure above 55 decibels.

Noise exposure was modeled based on a list of all aircraft movements at Zurich Airport from 2000 to 2015 in conjunction with existing aircraft noise exposure calculations. The different aircraft types, flight routes, as well as time of day and year were taken into account. "Previously, data from so-called noise footprints were used as the basis for long-term exposure calculations," explains Empa researcher Beat Schäffer from the "Acoustics / Noise Control" lab in Dübendorf. "This new study was the first to match instantaneous noise exposure at a specific time of day at a specific location with mortality data."

And indeed, the calculations were able to show a correlation between acute noise exposure and death rates. "We found that between the years 2000 and 2015, aircraft noise was the cause of approximately 800 out of 25,000 deaths from cardiovascular failure near Zurich Airport. This corresponds to about three percent of all observed cardiovascular deaths," says Martin Röösli of Swiss TPH.

According to Röösli, the results show that aircraft noise can have similar effects on cardiovascular mortality as emotions such as anger or excitement. "The results are not surprising, because we know that exposure to noise at night causes stress and affects sleep," he explains. In areas with little rail and road traffic noise, the impact of nighttime aircraft noise was even more pronounced. This was also true for residents of older, less noise-insulated homes.

The study used a so-called case-crossover design to determine whether aircraft noise exposure at the time of the deaths was abnormally high compared to randomly selected control periods. "This study design is very useful when you want to study acute effects of noise exposure with high daily variability, as in the case of aircraft noise due to changing weather conditions or flight delays," says Apolline Saucy of Swiss TPH. "With this temporal analysis approach, we can separate the effect of unusually high or low noise exposures on mortality from other factors. Factors related to lifestyle, such as smoking or poor diet, do not represent a bias in this study design."

Meanwhile, the study does not allow for a comparison of the effects of aircraft noise with other noise sources such as road and rail noise. "The relationship between aircraft noise and mortality rates is so amenable to study because of the exceptionally detailed data available for this mode of transport, and because there are large differences in noise exposure from day to day depending on weather conditions, unlike other modes of transport. However, there is no reason to assume that the observed correlations do not also apply to other types of noise," says Empa’s Schäffer.