An article on the harmful health effects of annoying noise was published recently in TheScientist by two German world-leading researchers (1). The authors give an overview of the topic in relation to the indirect, non-auditory effects on the cardiovascular system based on epidemiological and experimental mechanistic studies. Noise is defined as unwanted sound associated with annoyance reactions and disturbance of sleep. In 2011, the World Health Organization (WHO) concluded that exposure to transportation-related noise, in particular from aircraft, vehicles, and trains, is responsible for the annual loss of up to 1.6 million cumulative years of healthy life among people in Western Europe.
Though there is no set noise threshold or limit to establish risk, it is possible that noise above 60 decibels can increase risk for heart disease. This low-level noise occurs in conversations, the sound of a dishwasher or the noise from an air conditioning unit, and may have negative effect on communication, concentration, daily activities and sleep, which again may cause annoyance, mental stress and activation of the sympathetic nervous system and stress hormones. It seems that the cardiovascular side effects of noise are greater in those who get a stronger annoyance reaction, as they are getting more increased stress responses compared to those who are not so annoyed.
When nightly noise leads to impaired sleep and elevation of stress hormone levels, the result may be increased oxidative stress in the cerebral blood vessels. The biological mechanisms may be linked to noise activating the brain’s limbic system, which partly regulates the emotions, the stress hormone release and the control of the sympathetic nervous system. Another mechanism is that disturbed sleep can cause cognitive and emotional responses via activation of the amygdala. These various responses can lead to vascular dysfunction, inflammation and hypertension, which may increase the risk of cardiovascular disease. Chronic stress due to years of noise exposure can also cause high cholesterol, high blood glucose, increased blood viscosity, blood coagulation and inflammatory reactions leading to endothelial dysfunction, increased production of reactive oxygen species in the vascular wall, and plaque buildup. Acute noise stress seems to be able to cause plaque rupture.
There is good epidemiological evidence that long time exposure from traffic noise increases the risk of coronary heart disease by eight percent. Further, from clinical and experimental studies it is shown that noise is associated with cardiovascular conditions such as hypertension, stroke, heart-related mortality and premature deaths. Field and experimental studies with translational approach have shown that people and animals who were exposed to frequent, loud noise also had higher rates of heart failure, atrial fibrillation, high cholesterol and high blood glucose.
The EAPC President, Martin Halle, has emphasised improvement of risk factors as one of the key strategic focal points. Environmental noise is indeed preventable. Politicians and stakeholders need to collaborate with researchers, health workers and those exposed to noise pollution in the process to reduce noise pollution through legislation. There are several knowledge gaps regarding the pathophysiological mechanisms, healthy noise limits and thresholds as well as possible noise mitigation actions. The research needs better understanding from the medical society and support from funding agencies and governments.