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Loud noise such as the honking of horns, heavy road traffic, live music, and noise from construction sites can be a source of stress or annoyance. However, health experts warned that everyday noise could also cause a higher risk of heart diseases.
German and Danish researchers reviewed years of data and analyzed past research to determine the link between noise and cardiovascular ailments. They found that people and even animals exposed to frequent, loud noise had higher rates of heart failure, irregular heart rhythms, hypertension, high cholesterol, and high blood sugar, ABC reported.
Surge in stress hormones
Noise pollution causes an increase in stress hormones that appear to have harmful effects on the arteries in the heart and other parts of the body, the researchers said. The new study, published in the Journal of The American College of Cardiology, did not prove that the cause of heart ailments is noise, but it provided convincing evidence that stress generated by noise is linked to major consequences to the health.
Similar to high cholesterol or obesity, noise pollution should be considered a risk factor for heart disease, Dr. Thomas Münzel, the lead author from the University Medical Center Mainz Center of Cardiology, said. He noted that it is known that for people who have pre-existing factors for heart ailments, such as high blood pressure or diabetes, the risk will be amplified by noise.
While there is no set threshold to establish risk, Münzel said that anything above 60 decibels can boost the risk for cardiovascular ailments. Among the noises above 60 decibels, according to the Decibel Scale provided by the World Health Organization, includes the ringing of the telephone (80 decibels), jackhammer (100 decibels), and a jet on takeoff (120 decibels).
Lack of clear consensus
Despite the WHO benchmark, there is no clear agreement on how much noise is considered dangerous for the heart. Münzel said more studies are needed to determine the duration of exposure to loud noise that makes it harmful. But he said it is known that the risk comes from years and years of exposure, not days.
He pushed for policy changes because while the medical community can acknowledge noise as a heart disease risk factor, since physicians and patients cannot regulate noise, governments must pay attention to the WHO noise limits. Then the governments can change the law accordingly.
A number of studies have shown that traffic noise increases the risk of heart diseases. Because noise is associated with oxidative stress, vascular dysfunction, autonomic imbalance, and metabolic abnormalities, the evidence from the study further strengthens the concept that transportation noise is a contributor to heart disease risk factors, Eureka Alert noted.
The study looked at the adverse effects of environmental noise on the autonomic nervous system and its consequences to the cardiovascular system, adverse cardiovascular effects of noise in humans, and in animals. The researchers likewise delved into some of the mitigation strategies used globally. The authors said that traffic management and regulation, the development of low-noise tires, and curfews for air traffic could help reduce noise, but other strategies are still required.
Consequences of noise on vascular function
MedicalResearch reported that to study the consequences of noise on vascular function, the authors did field studies where they exposed healthy people and patients with established coronary artery disease to jet, street, and railway noise. They measured the vascular function of the participants before and after exposure to the noise.
They then used the flow-dependent dilation methodology, combined with methods from the field of sleep research. The scientists said that since acute vitamin C administration improves vascular dysfunction induced by noise in healthy volunteers, they concluded that noise induced the formation of oxidative stress with the vasculature responsible for the phenomenon. An animal model developed allowed them to identify the enzyme involved in the process.
The next step
The researchers said that the next step is to study up to what extent in particular nighttime noise is causing the vascular damage. Previous studies identified nighttime noise as the cause of arterial hypertension, coronary artery disease, and heart failure. The studies attributed the phenomenon mainly to very short sleep or fewer than six hours of fragmented sleep.
They also have plans to study the effects of transportation noise on the production of reactive oxygen species in the brain, particularly the frontal lobe where the areas important for memory and learning are found. In animal models, the scientists are studying the effects of noise on vascular function with cardiovascular risk factors, including diabetes mellitus, arterial hypertension, and hypercholesterolemia.
The researchers are also testing currently if mean decibel levels or peak decibel levels are more important with respect to vascular damage in patients who have established coronary artery disease and the effect on vascular function, inflammation, and production of reactive oxygen species of railway noise.
[메디컬리포트=Vittorio Hernandez 기자]