How noise pollution affects our heart: Study shows a range of cardiovascular diseases caused by noise

Although the gains of the industrial revolution have transformed human life, they have also left an adverse impact on our health and environment. The environmental pollution (and pollutants) that we so intensely debate must also now include noise pollution as another huge threat to our cardiovascular health, reports the European Cardiovascular Review.

A Harvard Medical School publication also cites a study carried out and published by the European Heart Journal in November 2019. It claims that “Long-term exposure to traffic noise has been linked to a greater risk of heart disease.” New research reveals additional clues about this connection.

Increase in decibel levels proportionate to an elevated risk of heart problems: 

Researchers studied nearly 500 adults over a five-year period and gathered traffic and aircraft noise data for each person’s home address. After adjusting for other factors that contribute to cardiovascular risk (including air pollution), they found that every 5-decibel increase in the average 24-hour noise level was associated with a 34% increase in heart attacks, strokes, and other serious heart-related problems.

By using a specialized brain imaging technique, researchers showed that higher levels of noise exposure were associated with increased activity in the amygdala, the area of the brain involved in processing stress, anxiety, and fear. Excess noise also increased inflammation in the arteries, a known trigger for cardiovascular problems.

It is estimated that environmental noise exposure contributes to 48 000 new cases of ischaemic heart diseases (IHD) or 156 000 DALYs in Europe each year.

Numerous studies link chronic exposure to such environmental noise to an increased risk of heart-related troubles. People living near the Frankfurt Airport, for example, have as much as a 7% higher risk of stroke than those living in similar but quieter neighbourhoods, according to a 2018 study that investigated health data of more than one million people. An analysis of nearly 25,000 cardiovascular deaths between 2000 and 2015 among people living near Switzerland’s Zurich Airport saw significant increases in night time mortality after airplane flyovers, especially among women, a team reported recently in the European Heart Journal.

Sequence of noise’s cardiovascular effects:

1. When sound reaches the brain, it activates two important regions – the auditory cortex, which interprets noise, and the amygdala, which manages emotional responses to it.

2. As the noise gets louder, and especially during sleep, the amygdala activates the body’s flight-or-fight response – even if the person isn’t aware of it. One can feel anxious even while asleep and not realise its full impact.

3. Once initiated, this stress response releases hormones such as adrenaline and cortisol into the body. Some arteries constrict, others dilate, blood pressure rises, digestion slows while sugars and fats flood the bloodstream for quick use by the muscles.

4. The cascading stress response also prompts the creation of harmful molecules that cause oxidative stress and thereby, dramatic changes to the endothelium, the inner lining of arteries, and blood vessels.

5. This lining can go from a healthy state to one that’s “activated”, and inflamed, with potentially serious ramifications.

6. The person affected lands up with a range of cardiovascular illnesses, including high blood pressure, plaque build-up in the arteries, obesity, and diabetes.

A recent study by Halonen et al. involving over 8 million people in London, assessed the effects of long-term exposure to road traffic noise on both all-cause and cardiovascular mortality and on hospital admissions for cardiovascular disease. The study, which looked at both younger and older subjects, showed that long-term exposure to road traffic noise was associated with an increased risk of all-cause mortality and cardiovascular mortality and morbidity in the general population; showing a prevalence of stroke particularly high in the elderly.

According to the European Cardiology Review, noise pollution can affect sleep patterns and the latter is known to be associated with increased cardiovascular morbidity and mortality. Studies on people and mice show that the endothelium doesn’t work as well after just a few days of nighttime airplane noise exposure, suggesting that loud noise isn’t a concern only for people already at risk for heart and metabolic problems. Healthy adults subjected to train recordings as they slumbered had impaired blood vessel function almost immediately, according to a 2019 study.

Thankfully, there is a growing recognition of the connections between noise pollution and reduced physical health. A 2018 report by the WHO noted that each year, western Europeans are collectively losing more than 1.6 million years of healthy life because of traffic noise. This calculation is based on the number of premature deaths caused directly by noise exposure as well as the years lived with noise-induced disability or illness.

And that number is likely to grow. In 2018, 55%of people lived in cities, and by 2050 that count is expected to reach nearly 70%, the United Nations estimates.

What is the acceptable level of noise?

Estimates suggest that roughly a third of people in Europe and the US are regularly exposed to unhealthy levels of noise, typically defined as starting around 70 to 80 decibels. For comparison, normal conversation is typically about 60 dB, cars and trucks range around 70 to 90 dB, and sirens and airplanes can reach 120 dB or more. The WHO has identified a threshold of >55 dB as a level of noise that is associated with health problems and very large numbers of individuals across the whole age spectrum are affected by traffic noise in cities in the developed world.

Policy changes around noise pollution:

• Some governments have begun considering night time flight bans

• Corporate set-ups are incentivising quieter technologies

• Civic authorities are issuing fines for noise complaints

What individuals can do:

• Ensure that bedrooms are as quiet as possible

• Retrofit windows or hang noise-reducing curtains

• If one can afford, move to quieter neighbourhoods

• Cheaper solutions may be wearing earplugs at night

• Moving bedrooms to a quieter part of the house

A word of caution: Just because you are considering a noisy environment as the new normal or are unfazed by noise, does not mean your heart is fine with that. If you have habituated to it psychologically, it doesn’t cancel out the negative health consequences.