1 point by karyan03 1 month ago | flag | hide | 0 comments
It is a common misconception that sleep is a state of complete rest where all senses are shut down. This is far from the scientific truth. The auditory system, in particular, is a sensory organ that remains on high alert 24/7, even while we are asleep.1 Unlike our eyes, which can block visual information by closing the eyelids, our ears continuously collect and process external sound information. This is a primal defense mechanism that evolved to detect potential danger signals, such as the approach of a predator or a baby's cry, to ensure survival.2
In the past, it was thought that the brain simply 'ignored' most sounds during sleep. However, recent research has revealed this process to be a much more sophisticated and active neural activity. A research team from the Korea Advanced Institute of Science and Technology (KAIST) has made a groundbreaking contribution to our understanding of this field by identifying a new neural circuit that responds to sound while an animal is sleeping.2
According to their research, the 'Medial Geniculate Thalamus' plays the primary role in processing sound information when we are awake. However, during deep sleep, or Non-REM sleep, the nerve cells in this auditory thalamus also cease their activity and 'go to sleep'.2 At this very moment, the brain activates an alternative pathway. Sound signals are transmitted through the brainstem to another brain region called the 'Mediodorsal Thalamus'.2 The researchers discovered that specific neurons within this mediodorsal thalamus, particularly those with the 'GRICK4' gene, play a key role in responding to sound and awakening the brain.2
The discovery of this dual-pathway system signifies a fundamental paradigm shift in understanding the effects of noise during sleep. It shows that the brain does not simply ignore or block sounds during sleep but actively monitors and processes them through a separate, dedicated neural network. This means that all the sounds we are unaware of—the TV sound, road noise, the subtle hum of a refrigerator—are constantly being analyzed by the sleeping brain, which has the potential to degrade sleep quality and trigger a physiological stress response. Therefore, the problem of noise during sleep must be approached not just as a matter of potential damage to the auditory organs, but as a problem of chronic neural stimulation and its consequent systemic health issues. Based on these latest neuroscientific findings, this report aims to conduct an in-depth analysis of the direct impact of sleeping with the TV on hearing loss, as well as its broader and more severe effects on sleep quality, stress responses, the cardiovascular system, and other auditory disorders.
To understand the mechanism of Noise-Induced Hearing Loss (NIHL), one must first understand the process of sound processing. Sound, which is the vibration of air, enters the ear canal through the pinna and vibrates the eardrum. This vibration is amplified by three small bones in the middle ear (the ossicles) and then transmitted to the cochlea, located in the inner ear.1
Inside the cochlea are hair cells, which play a crucial role in hearing. These delicate hair cells are sensory receptors that convert mechanical vibration energy into electrical signals that the brain can interpret.4 The problem is that these hair cells are extremely fragile and do not regenerate once damaged. Excessively loud noise generates powerful acoustic energy that can physically damage or destroy the hair cells.4 Damaged hair cells can no longer transmit sound signals to the brain, which leads to permanent sensorineural hearing loss.
In the initial stages of noise exposure, a phenomenon called 'Temporary Threshold Shift' occurs, which is characterized by a feeling of fullness in the ears and temporary difficulty in hearing. While hearing can be restored with sufficient rest, repeated occurrences of this temporary damage eventually lead to a 'Permanent Threshold Shift,' which is permanent hearing loss.5
The risk of developing NIHL is determined by two key variables: 'sound intensity' and 'exposure duration'.5 This is a kind of 'dose-response relationship,' where the louder the sound and the longer the exposure time, the risk of hearing damage increases exponentially.
Global industrial health organizations such as the World Health Organization (WHO) and the U.S. National Institute for Occupational Safety and Health (NIOSH) have set noise exposure standards to protect workers' hearing. The most widely accepted standard is to maintain a noise level below $85 \text{ dB(A)}$ for an 8-hour workday.4
What is important here is the '3-dB exchange rate.' This is the principle that for every $3 \text{ dB}$ increase in noise intensity, the permissible safe exposure time is halved. For example, 8 hours of exposure is allowed at $85 \text{ dB}$, but this time is drastically reduced to 2 hours at $90 \text{ dB}$, 15 minutes at $100 \text{ dB}$, and less than 1 minute at $115 \text{ dB}$.5 For everyday environmental noise, a safe level that does not cause hearing damage is generally considered to be below
$75 \text{ dB}$.9 Noise exceeding
$130 \text{ dB}$ can cause immediate pain and permanent hearing damage with just a single exposure.5
Understanding these decibel levels in the context of daily life is crucial for assessing one's own auditory environment. The following table provides specific examples of various noise levels and their corresponding health risks.
| Decibel Level (dB) | Common Examples 5 | Permissible Exposure Limit (WHO/NIOSH) 5 | Potential Health Effects 17 |
|---|---|---|---|
| $30 \text{ dB}$ | Whisper, quiet room, wall clock ticking | Safe | Pleasant level |
| $40 \text{ dB}$ | Library, quiet residential area, refrigerator hum | Safe | Sleep disturbance may begin above $40 \text{ dB}$ |
| $60 \text{ dB}$ | Normal conversation, office noise, sewing machine | Safe | Sleep disturbance begins above $60 \text{ dB}$ |
| $70 \text{ dB}$ | Vacuum cleaner, downtown traffic, telephone ringing | Generally safe | Peripheral vasoconstriction, increased stress with prolonged exposure |
| $85 \text{ dB}$ | Noisy intersection, inside a subway, truck noise | Risk of hearing damage with more than 8 hours of exposure | Risk of hearing damage begins, increased cardiovascular strain |
| $90 \text{ dB}$ | Lawn mower, construction site noise, personal audio devices | Risk of hearing damage with more than 2 hours of exposure | High risk of hearing damage |
| $100 \text{ dB}$ | Chainsaw, rock concert, karaoke, train noise | Risk of hearing damage with more than 15 minutes of exposure | Serious risk of hearing damage |
| $120 \text{ dB}$ | Ambulance siren, thunder, nightclub | Immediate danger | Can cause pain, damage possible even with short-term exposure |
| $140 \text{ dB}$ | Gunshot, jet engine takeoff | Immediate damage | Immediate pain and permanent hearing damage |
The $85 \text{ dB}$ standard was primarily established to protect workers in industrial settings and does not perfectly reflect the risk of chronic, low-intensity noise exposure that occurs daily for 8 hours during sleep. Recent studies and legal precedents are questioning the very concept of a 'safe' noise level.
A noteworthy case is a court ruling that recognized a worker's noise-induced hearing loss as an industrial accident after long-term exposure to noise between $75.7 \text{ dB}$ and $80.1 \text{ dB}$ in the workplace.20 This indicates that the court acknowledged not only the absolute threshold of
$85 \text{ dB}$ but also the 'duration' of noise exposure as a significant cause of hearing loss. Such a ruling suggests that even low-intensity noise can cause serious hearing damage with chronic exposure over decades.
Scientific research also supports this. One study reported that temporary hearing loss could be observed in the most acoustically sensitive $4000 \text{ Hz}$ frequency band even after 24 hours of exposure to noise levels of $75 \text{ dB}$ to $80 \text{ dBA}$.21 This implies that chronic noise exposure lasting more than 8 hours, such as sleeping with the TV on, carries a non-negligible risk of cumulative damage, even if the intensity does not reach
$85 \text{ dB}$.9 Therefore, it is important to keep in mind that even noise below the safety standard can lead to permanent damage if repeated over a long period.
To assess the risks of sleeping with the TV on, we must first accurately understand the noise environment created by a television. TV noise can be broadly divided into two categories: the operational noise of the TV itself and the audio output from its speakers.
Let's now answer the core question: Can the habit of sleeping with the TV on cause noise-induced hearing loss? The answer depends on the volume and duration of exposure, and it is important to first recognize that other health risks are far greater than the risk of direct hearing loss.
In conclusion, if a healthy person sleeps with the TV volume kept very low and stable, the likelihood of experiencing direct hearing loss is low. However, this is by no means a 'zero-risk' activity. Years of exposure to high volumes or sudden changes in sound clearly carry a risk of cumulative damage that is difficult to quantify.
However, there is a crucial fact that must be pointed out here. The user's concern about the possibility of hearing loss is, in fact, more of a 'red herring' that distracts from a larger and more immediate danger. The most serious harm of sleeping with the TV on is not auditory damage, but the degradation of sleep quality and chronic stress responses that occur at much lower noise levels, and the resulting collapse of systemic health. While concern about hearing loss is valid, one must first pay attention to the silent assault on the heart, brain, and metabolism.
Sleep is not simply a state of unconsciousness. It is a complex process in which several stages cycle in a sophisticated manner, broadly consisting of light sleep, deep sleep (NREM stage 3), and REM sleep. Each stage performs its own important functions, such as physical recovery, memory consolidation, and emotional regulation.26
Noise during sleep is a major culprit that destroys this delicate sleep architecture. Noise continuously stimulates the brain, shortening the duration of deep sleep and REM sleep, which are most important for physical and mental recovery.26 Because of the noise, the brain remains in lighter, lower-quality sleep stages, which severely impairs the restorative functions of sleep. As a result, no matter how long you spend in bed, you wake up feeling unrefreshed and groggy in the morning.26
Noise does not have to wake you up completely to be harmful. Even if you don't wake up, noise can trigger a phenomenon called 'micro-arousal.' This is an unconscious reaction where brainwaves briefly shift from a sleep state to an awake state, which you are not aware of yourself.28
When these micro-arousals are repeated throughout the night, sleep becomes a state of 'sleep fragmentation,' where sleep is broken into pieces. This destroys the continuity of sleep, causing the recovery process that takes place during deep sleep stages to be constantly interrupted and restarted. A person sleeping may not even remember tossing and turning all night, but their sleep quality is already severely compromised.26 The alternative auditory pathway of the mediodorsal thalamus mentioned in the introduction provides neurological evidence for how these micro-arousals occur.2
Poor-quality sleep caused by noise leads to a wide range of negative consequences.
There is an important point that many people overlook here: the illusion of 'habituation to noise.' Many people believe they have "gotten used to" sleeping with the noise of the city or the TV on. While it is possible to become somewhat desensitized to noise psychologically, the physiological response never completely disappears. Studies show that even after years of exposure to noise, the body continues to show physiological responses such as changes in heart rate or secretion of stress hormones in response to sound stimuli.26 In other words, even if the noise is no longer consciously bothersome, our bodies are experiencing a silent stress response all night long. Therefore, the subjective feeling that "I'm fine because I'm used to the noise" cannot be a reliable indicator for judging one's health status, and it is important to recognize that potential damage is continuously accumulating unconsciously.
The most destructive effect of noise exposure during sleep spreads throughout the body via the stress response. Noise heard during the vulnerable state of sleep is interpreted by the brain as a potential threat signal. This immediately activates the sympathetic nervous system, which governs the body's 'fight-or-flight' response.32
When the sympathetic nervous system is activated, the adrenal glands release stress hormones such as adrenaline and cortisol into the bloodstream.28 This is not just a psychological feeling of 'being stressed,' but a powerful and measurable hormonal and neurological event that affects the entire body.32
This stress response delivers a direct and deadly blow to the cardiovascular system. It is crucial to trace the path by which the habit of sleeping with the TV on can lead to life-threatening diseases.
The secreted stress hormones cause immediate physiological changes. The heart rate increases, blood pressure rises, and the skin and peripheral blood vessels constrict.32 When this response is repeated every night, a temporary rise in blood pressure develops into chronic hypertension, and the delicate endothelial cells lining the blood vessels suffer continuous damage.28
Cholesterol and inflammatory cells begin to accumulate on the damaged vessel walls, which promotes atherosclerosis, the buildup of plaque in the arteries. Atherosclerosis is the underlying cause of most heart attacks and strokes.32
This association has been clearly demonstrated through large-scale epidemiological studies. A representative study of residents near major airports showed shocking results. People heavily exposed to aircraft noise showed negative changes in heart structure, such as a significant increase in heart mass and thickness, and had a four times higher risk of suffering a heart attack, stroke, or arrhythmia compared to those who were not.28 The World Health Organization (WHO) and the European Environment Agency (EEA) have also officially concluded that chronic noise exposure is a major environmental factor that causes cardiovascular disease and premature death.33
This mechanism is similar to what is seen in patients with sleep apnea. Sleep apnea patients experience repeated hypoxia and arousals during sleep, which, like micro-arousals caused by noise, stimulate the sympathetic nervous system and induce oxidative stress and inflammatory responses. This has been shown to damage the auditory nerve and blood vessels, increasing the risk of both hearing loss and cardiovascular disease simultaneously.36
The effects of chronic stress caused by noise are not limited to the cardiovascular system.
Taking all this evidence together, chronic nocturnal noise exposure is no longer a matter of minor inconvenience. It should be classified as a major modifiable lifestyle risk factor that causes cardiovascular disease, just like a poor diet, smoking, and lack of exercise. Just as doctors advise patients to control their diet and exercise, creating a healthy sleep acoustic environment should also be considered an important preventive medical prescription. Therefore, the following recommendations should be understood not as mere 'tips,' but as essential health management strategies to protect long-term health.
Tinnitus is a symptom of perceiving a specific sound, such as a 'ringing' or 'buzzing' sound, in the ears or head in the absence of an external sound stimulus.37 Tinnitus is not a disease in itself, but rather a symptom that accompanies other underlying conditions.
The relationship between noise during sleep and tinnitus is multifaceted and complex.
The mechanism of tinnitus is thought to be related to the brain's compensatory action. When the external sound signal entering the brain is reduced due to hearing loss, the auditory cortex of the brain abnormally increases the 'gain' or 'volume' of its own neural activity to compensate. In this process, it creates a sound that does not exist, which is tinnitus.40 The state of brain hyperarousal caused by poor quality sleep serves to amplify this false signal.
Hyperacusis is a condition in which everyday sounds that most people do not find uncomfortable are perceived as unbearable and painful.42 Misophonia is a condition in which a person feels a strong aversion and anger towards specific sounds, such as chewing or breathing sounds.42
The 'abnormal auditory gain' theory is most widely accepted as the core mechanism of these symptoms.43 This means that the brain's auditory system produces an abnormally excessive neural excitation in response to the intensity of the incoming sound signal, in other words, the brain's 'volume control' is broken and is excessively amplifying.
Chronic nocturnal noise and stress play an important role in causing or exacerbating this condition. The constant stress and lack of sleep caused by noise put the nervous system in a state of 'hyper-vigilance,' which is extremely sensitive and alert. In this state, the threshold at which the brain perceives sound as a threatening or overwhelming stimulus is lowered, causing an overreaction to sounds that were previously not bothersome.42 A vicious cycle can even form where the fear of the sound itself causes further stress, making the auditory system even more sensitive.45
In conclusion, tinnitus and hyperacusis are not simply 'ear problems.' They are evidence of 'maladaptive neuroplasticity' of the nervous system, where the brain has adapted incorrectly to the stimuli of hearing loss and chronic stress. The chronic nocturnal noise caused by habits such as sleeping with the TV on provides all the conditions of hearing loss, stress, and lack of sleep, thus creating an optimal environment for the brain to fall into and maintain this pathological state.
Using earplugs to effectively block external noise is an excellent method. However, not all earplugs provide the same performance, so it is important to choose a product that suits your needs.
Refer to the following table to select the optimal earplugs for your sleep environment and needs.
| My Sleep Environment / Needs | Recommended Earplug Type | Key Considerations | Rationale and Considerations |
|---|---|---|---|
| Living in a city with heavy traffic noise | High NRR Foam Type Earplugs | NRR $30 \text{ dB}$ or higher, Class 1 (EP-1) grade | Maximum noise reduction is needed to effectively block low-frequency vehicle noise. Proper insertion technique is essential. |
| Partner's snoring | Moldable Silicone Type Earplugs | Perfect seal at the ear canal entrance | Provides a perfect fit tailored to your ear shape to effectively block the specific frequencies of snoring. Less feeling of a foreign object. |
| Very sensitive sleeper | Low-Pressure Foam Type Earplugs | Soft material, comfortable fit | Minimizes discomfort by applying less pressure on the ear, even when worn all night. A balance between sound reduction and comfort is important. |
| Use during travel and business trips | Flanged Type Reusable Earplugs | Portability, easy insertion/removal | Easy to carry and manage hygienically. Choose a product that comes with a case. |
The methods presented above are part of a larger picture. For healthy sleep, an integrated management approach is necessary.
This report began with the simple question, "Can sleeping with the TV on cause hearing loss?" and has conducted an in-depth analysis of the multi-layered and severe threats that nocturnal noise poses not only to the auditory system but also to systemic health, including sleep, the nervous system, and the cardiovascular system.
The analysis clearly confirmed that the key risk of the habit of sleeping with the TV on lies not in direct hearing damage, but in the destruction of sleep architecture and chronic stress responses that begin at much lower noise levels. The brain remains awake to process sound even during sleep, and the resulting micro-arousals and over-activation of the sympathetic nervous system attack our bodies all night long. When this process is repeated for years, it increases the risk of fatal diseases such as hypertension, atherosclerosis, heart attack, and stroke, and provides the soil for exacerbating painful auditory disorders like tinnitus or hyperacusis.
In conclusion, actively managing the acoustic environment of the bedroom is no longer a matter of comfort or preference. It is an essential investment for long-term health and well-being, and a key practice of preventive medicine based on scientific evidence. Making the sleep timer a daily habit, using earplugs if necessary, and wisely utilizing noise-masking sounds should be recognized not just as an effort to get a 'good night's sleep,' but as an important health management act to protect one's heart and brain. The quiet of the bedroom is one of the most powerful health supplements we can give ourselves.