New research looking at long-term exposures to road traffic noise and ambient air pollution found significant associations between pollutants and high-sensitivity C-reactive protein (hsCRP), blood lipids and fasting glucose. The research published in the European Heart Journal suggests a possible link between road traffic noise/air pollution and cardiometabolic disease risk.

The population-based study included 144,082 participants with a mean age of 47.6 years, 56 percent of whom were women. Road traffic noise exposure was modelled using a simplified version of the Common Noise Assessment in Europe (CNOSSOS-EU), while annual ambient air pollution (PM10, NO2) at residence was estimated using a Land Use Regression model. Researchers used generalized linear models to assess cross-sectional associations between pollutants and hsCRP, high-density lipoprotein (HDL), triglycerides and fasting glucose.

Results found that an inter-quartile range (IQR) higher day-time noise (5.1 dB[A]) was associated with 1.1 percent higher hsCRP, 0.7 percent higher triglycerides and 0.5 percent higher HDL. An IQR higher air pollution was associated with higher triglycerides (1.9 percent). Additionally, an IQR higher noise and air pollution was associated with 0.2 percent and 0.6 percent higher fasting glucose, respectively.

Researchers noted only the associations of higher HDL cholesterol and fasting glucose were robust enough to remain after adjustment for both noise and air pollution. "Analysing noise as a categorical variable suggested that there may exist a threshold of 60 dB(A), above which a significant positive association on hsCRP was seen in our study," they write. "However, significance was lost after adjustment for air pollution."

The study's findings further contribute to ongoing research efforts to identify potential mechanisms and quantify impacts of both road noise and air pollution on cardiovascular disease. According to the authors, "future work will explore potential for effect modification and whether effects are confined to a subset of the population."

In a related editorial comment, Thomas Munzel, MD, et al., agree that more research is needed and note there are many question that still need to be addressed, including "assessment of the magnitude and time course of the response to joint noise and air pollution exposure; interactive effects of both exposures on, for example blood pressure, blood lipids, and measures of metabolic risk; duration of effect and time course of reversal; impact of low-grade background noise on air pollution exposure effects, and vice versa; impact of noise-induced sleep disturbance on effects of air pollution; and finally the effect of prevention and lifestyle (e.g., diet, stress, and exercise)." They go on to say that "elucidating whether co-exposure to both noise and air pollution have combined effects on a mechanistic level is important to help us understand the interplay between these highly frequent environmental exposures in relation to human health."

Keywords: Air Pollution, Blood Pressure, Cardiovascular Diseases, Cholesterol, HDL, Environmental Exposure, Europe, Hypertriglyceridemia, Linear Models, Lipoproteins, HDL, Noise

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