As seen in Psychology Today.

When we think of pollution, we often think of things like litter, smog, and toxic waste. We also tend to think of certain types of pollution as affecting certain organs. As a very clear example, we recognize that poor air quality can impact lung health, or that contaminated water and food can cause GI problems. The relationship is not ambiguous.

When we start to talk about other forms of pollution, such as light pollution or noise pollution, their effects on the body become more abstract and the relationship more tenuous. True, very loud noises can certainly damage the ears and lead to tinnitus, but the notion that an individual’s overall health and well-being can be adversely affected by noise pollution over time seems unnecessarily alarmist. Unfortunately, there are signs that cause for alarm is warranted.

What Is Stress?

Stress is a part of life. It always has been, it always will be, and its prevalence has led many of us to think of it in vague or metaphorical terms. Perhaps we conceive of it as a sense of pressure. While this is common among people with and without medical backgrounds, there is a formal definition of stress as described by Tsigos and colleagues that I believe is clear and less abstract. For them, stress is “a state of threatened homeostasis triggered by intrinsic or extrinsic adverse forces (stressors).” The authors go on to note that stress is “counteracted by an intricate repertoire of physiologic and behavioral responses aiming to maintain, reestablish the optimal body equilibrium.”

Every organism encounters stress throughout their lives, but the important thing is that every organism has also evolved to respond to stress with coping mechanisms that bring their bodies back into this state of equilibrium or homeostasis. From bacteria to complex mammals like us, we have tools at our disposal to respond to stress, mitigate stressors, and restore balance.

In vertebrates, the stress response primarily falls under the domain of the autonomic nervous system (ANS), which regulates vital processes like heart rate, vasculature, and even sexual arousal through the release of stress hormones and other neurophysiological responses. It consists of two divisions: the sympathetic nervous system (SNS), which primes our body for danger, and the parasympathetic nervous system (PSNS), which brings us back to a state of relative calm once the threat has passed. The SNS is responsible for what’s known as the fight or flight response, while the domain of the PSNS is rest and digest.

There are far too many parts of the system to describe at length, but the central alarm system of the SNS does deserve special attention. Known as the hypothalamic-pituitary-adrenal (HPA) axis, it consists of a region of the brain known as the hypothalamus, the pituitary gland, and adrenal glands. These three components work in concert to trigger the hormonal and neurological cascade when we feel threatened and activate the SNS. We may believe that we have healthy coping mechanisms to deal with human problems, particularly those that manage deadlines and frustrations with modern technology, but the HPA axis still gets triggered no matter the source of the stress—even chronic and low-level stress.

This can become problematic. When stress becomes constant and overwhelming, the PSNS may not be able to bring the body back to homeostasis. Instead, the unresolved stress begins to manifest as oxidative stress and systemic inflammation, which can lead to hypertension, stiffened blood vessels, plaque buildup, and even psychological symptoms like anxiety and depression. If left unresolved, these problems can contribute to obesity and diabetes, as well as increase the risk of serious cardiovascular disease and even some autoimmune disorders.

Can Noise Cause a Stress Response?

The very simple answer is yes. It is also common. If you have ever been annoyed by noise, then you have most likely experienced a noise-related stress response.

More importantly, if simple exposure to noise caused all the problems noted above, we would be in deep trouble. Instead, the issue comes back to the idea of overload. We are overwhelmed by stressors that keep the SNS engaged—excessive noise is just one more annoyance. Noise itself is not doing the damage; it’s our emotional response to excessive noise that causes problems. If we weren’t bombarded by other stressors, it would likely not lead to an adverse emotional response or any of the adverse effects noted above.

These effects are more significant than one might assume. The World Health Organization quantified these problems in a 2011 report that concluded excessive transportation-related noise is responsible for an annual loss of 1.6 million years of healthy life just among people living in Western Europe. In 2015, the European Environmental Agency published a report linking excessive noise from transportation (cars, trucks, trains, and planes) to an additional 1.7 million cases of hypertension, an additional 80,000 hospital admissions, and an additional 18,000 premature deaths from coronary heart disease or stroke each year in Europe.

Yet another factor that can make excessive noise more pernicious is its timing. During the day, excessive noise can cause annoyance and contribute to stress. When it occurs at night, it adds to cumulative stress, but can also disturb one’s sleep cycle and disrupt the efforts of the PSNS to bring the body back to its baseline. Even if individuals are not disturbed to the level of waking up, noise can still lead to stress.

Turning Down the Volume

Unfortunately, eliminating excessive nighttime noise is beyond the scope of medicine and will require regulatory and legislative solutions. However, patients who recognize that noise pollution is causing an exaggerated stress response can mitigate the effects of oxidative stress by eating a diet that is rich in polyunsaturated fatty acids, fiber, Vitamin C, and polyphenols (compounds found in fruits and vegetables). They can also use white noise apps, wear earplugs, or add soundproofing to their bedrooms to muffle nighttime noises and give the PSNS the opportunity to reestablish homeostasis.