Effects of Noise Pollution on Increased Risk of Myocardial Infarction
Introduction
Noise is defined as unwanted sound. Environmental noise consists of all the unwanted sounds in our communities except that which originates in the workplace. Environmental noise pollution can be considered a threat to people's health and well being since it continues to become more severe and even more widespread because of population growth. Furthermore, urbanization happening all over the globe has increased the magnitude and severity of noise pollution that many people perceive it as an environmental stressor and a complete nuisance. 'Noise is an objectively quantifiable environment exposure that can trigger individual reactions and symptoms with the potential development of adverse health outcomes'. Since the early centuries of ancient Rome and Medieval Europe, people have been experiencing human-made environmental noise pollution, which is sometimes unavoidable because people have no control over the amount of noise pollution made by others.
Furthermore, environmental noise itself affects everyone in the vicinity, which includes men, women, and children. For example, in children, chronic aircraft noise exposure impairs reading comprehension and long-term memory and may be associated with raised blood pressure. Children exposed to long-term amounts of environmental noise pollution can also affect their ability to comprehend regular speech leading to future problems revolving around the development of personal disabilities or even behavioral changes. The problem a child could experience throughout their life could be having trouble concentrating, feeling fatigued or getting irritated by the smallest of noises, and a lack of self-confidence that could lead to a lack of motivation. As a result, an individual must avoid living in a house or avoid sending their child to a school that is surrounded by airports or highways since environmental noise pollution has a significant impact on an individual's cognitive development.
'Insight from epidemiological studies show that exposure to traffic noise from aircraft, road, vehicles, and trains is associated with increased cardiovascular morbidity and mortality. As a matter of fact, in Europe, traffic noise is responsible for 18,000 premature deaths, 1.7 million cases of hypertension, and 80,000 hospitalizations each year. In addition, exposure to traffic noise is associated with ischaemic heart disease (IHD) and is usually modeled using traffic intensity, traffic composition, speed, distance to roads, noise barriers and other factor input variables. When exposed to long-term environmental noise pollution people should start noticing signs of hearing impairment, interference in communication, sleep disturbances, cardiovascular disturbances, disturbances in one's mental health, impaired task performance and lastly a mix of both negative social behaviors and annoyance reactions as a defense mechanism to cope with noise pollution. Myocardial infarction is a cardiovascular disease that is also known as a regular heart attack. Myocardial infarctions usually occur when a particular portion of the heart is not receiving any oxygen because of a blockage of a coronary artery. Furthermore, the coronary arteries are essential since they supply the heart with oxygen; however, without oxygen, the muscle cells that were served by the artery will begin to die off, leading to myocardial infarction. In the height of all the negative consequences of noise pollution, this paper is going to focus on whether long-term noise pollution exposure causes cardiovascular diseases like myocardial infarction.
Methods
The research article my group chose is “Long-term Exposure to Road Traffic Noise and Myocardial Infarction,” written by Jenny Selander, Mats E. Nilsson, Gosta Bluhm, and et al. The hypothesis written in this article states that an increase in long-term exposure to road traffic noise increases the risk for myocardial infarction. The goal of their research is to determine that there has been an association reported between long-term exposure to road traffic noise and also a risk of getting myocardial infarction from environmental road traffic noise. The main focus of this study was to assess the risk for myocardial infarction concerning long-term exposure to environmental noise. The factors include road traffic noise and an assessment done of traffic-related air pollution with an additional set of risk factors that could potentially increase the chance for cardiovascular disease.
First of all, researchers wanted to record whether long-term exposure to road traffic noise caused myocardial infarction. They began this study based on a present study known as the Stockholm Heart Epidemiology Program conducted in Stockholm County. Both men and women who were inhabiting Stockholm County between 1992 and 1994 that age ranged from 45-70 years that had no history of myocardial infarction in the past are part of this study. The case also selected individuals from emergency hospitals who had already had their first myocardial infarction during 1992-1994. The individuals that chosen from emergency hospitals were gathered looking into specific areas like coronary records, hospital discharge registers, and even from the National Cause of Death register that is from Statistics Sweden. During this research assignment, the controls were selected at random using the following factors, which were age, sex, and hospital catchment area. In this experiment, they have a total of 5,452 study subjects that were split up into two different categories, which were 2,246 cases and 3,206 controls. Researchers decided to make a questionnaire that received a considerable amount of responses from women 72% and men 81%. Statistics showed that 603 individuals who died within the first 28 days of this experiment got classified as myocardial infarction fatalities. Individuals who had lived outside of Stockholm County got excluded, which left around 3,666 study subjects, which turned into two categories that were 1,571 cases and 2,095 controls.
Nonetheless, the questionnaire that was made and then distributed in 1992-1994 had focused on a variety of different risk factors for myocardial infarction. The risk factors included physical and psychological work environment, social factors, and even lifestyle factors that were activities like smoking and physical activity. In addition to the questionnaire, there was also a telephone interview to avoid problems like nonresponse individuals and missing data. The researchers wanted to gather as much information from their study group as possible, so they began looking at the biological parameters that were related to cardiovascular disease in both cases and controls. These examinations were performed around three months after the myocardial infarction onset. Uniquely, the data gathered through these biological variables were primarily on data recorded by the health examinations. The examination consisted of deriving hypertension to anti-hypertensive drugs, overweight to a body mass index of 27 kg/m2 or more, physical activity, smoking habits, air pollution exposure, socioeconomic status, and even job strain. The experiment progressed, and so did the assessment, which involved calculating the road traffic noise. The first method was known as the time-weighted average of A-weighted decibels (dBA). The values included variables like Li would be the sound level of road traffic noises, and Yi would be the number of years that a person resided in Stockholm County. The second method is known as the energy-based time-weighted average because it included people that were missing less than five years. Consequently, they had another supplementary questionnaire made, and this last one was distributed in 2003 to enhance the noise exposure assessment. The new questions included in the latest questionnaire were factors like hearing impairment, window insulation, bedroom orientation, and even noise annoyance.
The statistical methods provided by the author used the odds ratio and 95% confidence intervals using the unconditional logistic regression analysis. Not to mention that there was also analysis done for cases that were considered fatal and nonfatal using multinomial logistic regression. These calculations were calculated successfully due to an online statistical analysis program known as STATA.
Results
From the results, the authors were able to determine that smoking, physical inactivity, diabetes mellitus, and overweight was more common when it came to the people in the case group than the control group. However, there was also a similar tendency seen when it came to factors like job strain, occupational noise exposure, and hypertension. In the results, there seems to be an association between long-term exposure to air pollution and traffic noise pollution, which was a high correlation of 0.6 when it comes to these two variables. When examining myocardial infarction and road traffic noise exposure, it led to a subsample. The subsample in the paper explained that they excluded 1,207 people exposed to other noises or who had a hearing impairment then the myocardial infarction risk associated with road traffic noise had shown an increase according to how much it elevated. Overall though, they had found no difference between men and women, or whether someone was physically active or inactive, or people with or without diabetes mellitus. According to the odds ratio in the data collected that noise exposure was typically higher for the subjects that had a job strain compared to the subjects that did not have a job strain. Lastly, analyzing traffic noise exposure and myocardial infarction by using various variables with the help of the supplementary questionnaire was critical. It was crucial because it gave researchers a more profound understanding that there was an elevated risk of having high exposure to either air pollution or noise from road traffic causes myocardial infarction.
Conclusion
Selander and her colleagues who worked on this research concluded that long-term exposure to residential road traffic noise does increase the risk for myocardial infarction. The findings the researchers collected to support their hypothesis determined that individuals exposed to 50 dBA or higher since 1970, will have an increase in the risk for myocardial infarction compared to the other subjects who have had exposure of less than 50 dBA. The odds ratio had changed after they excluded people exposed to noise pollution from other sources that reported hearing loss. Similarly, people exposed to noise pollution were more annoyed and faced the issue of sleep disturbance. The subjects that were excluded from the experiment because they reported hearing impairments were because there is evidence that suggests that hearing loss may protect them against non-auditory health effects of occupational noise and residential aircraft noise as well. Subjects who had also reported noise annoyance mostly in their bedroom had an elevated increase in the risk for myocardial infarction. Given the points above, the author was also able to conclude that night-time noise exposure may be a specific health importance people need to take into consideration. The association with road traffic noise and myocardial infarction had shown more of an elevation in people with hypertension. Together with the data collected by the researchers, they were also able to pinpoint that the effect of road traffic noise on myocardial infarction has to be mediated by hypertension. Hypertension is also very well known for being a risk factor for cardiovascular diseases.
The barriers the authors did face were misclassification of disease that could be negligible in the present study because of strict diagnostic criteria, high reliability of case identification, and, most importantly, there is also a low probability of selection bias. There is also an issue that the road traffic noise data itself did not cover the relevant period in time, and the variation of where people lived was not a factor taken into consideration. The reason for this is because they used a simplified model that would be high validity, but would be less precise than other detailed methods. Moreover, they only measured residential areas even though traffic noise, in general, is everywhere around people.
Future research could mean taking into consideration some of the barriers and recording people over some time wherever they go to get a better estimate of noise pollution. The second option is to replicate the experiment itself to have it based on the relevant period in time to avoid using data from the past. Overall though, the author did not suggest any follow-up steps, but they did bring up previous studies done in the past and proved that they gathered different results.
