Noise, Stress Hormones and Health
Noise is a biological stressor. Excessive exposure to noise, as in aircraft or military aircraft noise, is a health risk and may be contribute to sleep disturbances, cardiovascular disease, hypertension, myocardial infarction, gastrointestinal disease, migraine headaches and immunotoxicity.
When looking at the body as a whole, it is easy to understand how environmental noise exposure disrupts the body’s homeostasis. Homeostasis defined is “a tendency of biological systems to maintain stability while continually adjusting to conditions that are optimal for survival.”
One core component of non-auditory related health effects begins with stress. Much of the reviewed research shows that prolonged environmental noise, especially aircraft noise, causes enormous stress.
Stress creates a cascade of releasing “fight or flight hormones” such as cortisol, adrenalin, epinephrine and norepinephrine which affect multiple systems in the body. When a person is exposed to loud noise a series of physiological responses occur:
- Adrenalin is released which increases the heart rate, blood pressure and breathing. Blood is shunted to the vital organs like the brain and heart, reduced in less vital areas like the gastro-intestinal tract, vasoconstriction occurs and muscles constrict, our mind becomes alert and focused.
- Continued releases of cortisol and other stress hormones leads to stress induced disease such as sleep disturbance, myocardial infarction, atherosclerosis and immunosuppression.
The immune system is a complex mechanism that keeps our body in homeostasis. Studies have shown that certain T cells (white blood cells that protect the body from disease organisms and other foreign bodies known as antigens) become suppressed with psychological stressors thereby reducing immunity.
Chronic stress also affects the inflammatory response, which raises the risk of viral infection. Stress has also been shown to exacerbate other diseases as well such as asthma and diabetes, and it increases the risk of certain gut conditions that affect the production of gastric acid thereby increasing the risks of ulcerative colitis, stress and peptic ulcers.
Studies About Aircraft Noise Impacts on Health
Studies about the effects of excessive noise are relatively new compared to other health issues, probably because we are experiencing more exposures to excessive noise today than ever before in history.
H. Ising (et al.) conducted one of the first noise studies involving military aircraft in 1990, in the Federal Republic of Germany; Munsterland and Franken. The document determined that the physical characteristics of military low-altitude flight noise are different in terms of other aircraft flight noise; the extremely high maximal sound level and the very rapid increase in sound level during direct over-flights combine to increase community annoyance and health symptoms.
They found that low altitude over-flight noise was associated with cardiovascular problems and sleep disturbances even during the “quiet” nights that follow over-flights.
In 2006, Ising updated the study with new information, and found the evidence had actually increased a great deal since 1990.
One study conducted by Meister and Donatelle (2000), using four neighborhoods exposed to commercial aircraft airports and two control group communities (no aircraft noise), found noise annoyance very stressful for the exposed neighborhoods. All health measures were significantly worse in the exposed communities than the control communities. This study confirmed the strong link between aircraft noise, stress load and decreased health consequences. It also confirms aircraft noise seriously affects a person’s sense of well being as measured by a “sense of vitality.”
Stress hormones are also sensitive to light and dark and awake-sleeping patterns consequently affecting our sleep. According to Prasher (2009), sleeping individuals cannot determine what the noise is so noise is therefore interpreted as “danger.”Aircraft noise is interpreted as danger, thereby effecting cortisol levels.
A study included in Deepak Prasher’s (2009) research found that even loud noise exposure during the day reduced effective sleep patterns down to 80%, and the rapid eye movement (REM) phase of sleep associated with dreaming was critically affected. Sleep is the time the body repairs and without it the body cannot survive.
Perhaps one of the most studied health effects of environmental and aircraft noise is cardiovascular disease. As mentioned prior, environmental and aircraft noise creates stress and chronic stress, which in turn increases the heart rate, pulse and blood pressure while creating vasoconstriction.
It also clogs the arteries with plaque causing atherosclerosis which often causes angina or myocardial infarction. The Los Angeles Airport Study determined that chronic exposure to aircraft noise raised systolic and diastolic blood pressure. These results were significant, even though the blood pressure numbers remained within normal limits.
Another study in Munich linked chronic noise exposure to both baseline systolic blood pressure and lower reactivity of the systolic blood pressure when doing a cognitive task under acute noise. After the new airport opened, a significant increase in the systolic blood press was noted, proving that there was a causal link between the airport noise and a rise in blood pressure.
One study (Huss, et al. 2010) used the Swiss National Cohort and the national census which included demographic data on where citizens lived as its cohort. The study included hospitalizations and ICD-9 codes in the identified areas. It also included 65 airports and airfields in Switzerland. Zurich, the largest airport, had a dedicated noise exposure model; the other 64 used an exposure model from the Federal Office of Civil Aviation.
The study was adjusted for confounders, and it was determined that acute and chronic noise exposure, in particular aircraft noise, is associated with high blood pressure, heart attacks, increased cardiovascular medication and cardiovascular morbidity and mortality. The risk of death from heart attacks was higher in individuals exposed to aircraft noise of 60 dB(A) or more.
Lastly, a multi-airport study of approximately 6 million older people residing near airports in the United States was conducted in 2009. The researchers used ICD-9 codes from hospital admissions to determine if groups exposed to commercial aircraft around commercial airports were at higher risk for negative cardiac outcomes, and despite limitations related to potential misclassification of exposure, there was a statistical significance relating airplane noise and cardiovascular disease related hospitalizations among older people living around airports.
Many of these studies were conducted around airports, and their results were troubling enough; when the fact that military aircraft noise is considered worse than a typical airport, increasing all the effects listed, the results are absolutely frightening.