How Your Brain Preserves Hearing While You Sleep

Hearing loss and sleep quality are closely linked, with studies showing that sleep issues increase the risk of hearing loss. While the exact nature of the connection is not yet fully understood, it is clear that the two have a significant impact on each other. For example, people with hearing loss are more likely to experience insomnia, and those with sleep apnea are more likely to suffer from hearing impairment.

Hearing while sleeping

It turns out that we can hear while we sleep! Our brains are more responsive than we think as we drift off, and we can actually hear during the lighter stages of sleep. However, as we enter REM sleep, our brain stops paying attention to the outside world.

Sleep Stages

There are four stages of sleep that we cycle through several times a night.

• Stage 1: The beginning of dozing off. The body is not yet completely relaxed, and it is very easy to wake up during this stage.
• Stage 2: Heart rate, breathing, and temperature drop. Brain waves slow down, and it becomes harder to wake up.
• Stage 3 (deep sleep): Critical for health and healing, this stage boosts the immune system and helps with memory consolidation.
• Stage 4 (REM sleep): The brain is very active, almost as much as when awake. This stage is important for cognitive functions, learning, and creativity, and it is when vivid dreams occur.

Hearing and Brain Activity

A 2019 study found that even during sleep, the brain pays attention to sounds and can distinguish between meaningful speech and gibberish. Another study showed that participants could process words heard during short, light naps. However, once they entered deep sleep, they could no longer process external sounds, and their brains started to ignore them.

Hearing Loss and Sleep

There is a definite link between hearing loss and sleep problems. Hearing loss can lead to insomnia, and sleep deprivation can exacerbate hearing issues. Sleep apnea, a condition that interrupts breathing during sleep, is also linked to hearing impairment. Additionally, hearing loss can impact sleep quality by causing stress, mental fatigue, and tinnitus.

Improving Sleep with Hearing Aids

Hearing aids can improve sleep quality by reducing stress and mental fatigue associated with hearing loss and, in some cases, minimizing tinnitus symptoms. They can also improve social connections, which can reduce depression and improve sleep.

Sleep stages and hearing

Sleep is divided into four stages, which we cycle through several times a night. Each stage has a different impact on our hearing.

In the first stage, we start to doze off, and it is very easy to wake up during this stage. Our bodies are not completely relaxed yet, and we may experience some body twitches.

In the second stage, our heart rate, breathing, and temperature drop, and our brain waves slow down. It is harder to wake up during this stage.

The third stage is deep sleep, during which our brain disconnects from the outside world. We are less likely to hear external sounds or be disturbed by noises in the environment. Our brain consolidates memories from the day and stores them in our long-term memory.

The fourth stage is REM (rapid eye movement) sleep, during which we often start dreaming. All the brain activity that paused in the third stage starts again as we dream. However, we still do not process exterior sounds during this stage.

During the first two stages of sleep, we can hear and process sounds in our environment. A 2016 study found that during light sleep, we are still processing the things we hear and can even hear and process new words. EEG readings showed that participants' brains were responding to words and continuing verbal recognition tasks they had started when awake. However, as we transition into deep sleep, we stop processing external sounds.

Sleep problems and hearing loss

A study published in the September/October 2023 issue of *Ear and Hearing* found that sleep issues raised the risk of hearing loss, and the more sleep problems a person had, the greater the risk. The study also found that people who consistently slept less than the recommended seven to nine hours per night experienced more hearing loss.

Obstructive sleep apnea, a common sleep disorder, has also been linked to an increased likelihood of hearing loss. Sleep apnea causes reduced oxygen in the bloodstream, which damages the delicate inner ear hair cells responsible for hearing. Additionally, people with sleep apnea wake up throughout the night, leading to poor or reduced amounts of sleep.

Hearing loss can also contribute to sleep problems. People with hearing loss must work harder to discern between sounds, a skill that requires core auditory processing. A lack of sleep can exacerbate listening fatigue as the ears have less time to recuperate.

Furthermore, tinnitus, a condition characterised by a ringing in the ears, is often associated with hearing loss and can disrupt sleep. Treating tinnitus with a combination of psychotherapy and sound therapy can help improve sleep quality.

Hearing aids can also help improve sleep quality for people with hearing loss. A study found that using hearing aids during the day helped people with hearing loss sleep better at night.

In summary, the relationship between sleep problems and hearing loss is complex and bidirectional. Addressing sleep problems and hearing loss through proper treatment and interventions can help improve overall health and well-being.

Sleep apnea and hearing loss

While we sleep, our brains continue to process sounds from the environment, depending on the sleep stage we are in. During light sleep, we are more likely to hear noises and wake up. However, during deep sleep and REM sleep, we are less likely to hear external sounds and are more focused on our dreams.

Now, regarding sleep apnea and hearing loss, there seems to be a strong link between the two. People with sleep apnea are 21% more likely to have hearing impairment, according to a study. Obstructive sleep apnea (OSA), the most common type of sleep apnea, occurs when muscles and tissues around the airway relax and block breathing, causing snoring and frequent waking. Sleep apnea affects blood flow to the ears, which need a good blood supply to function properly. Additionally, years of loud snoring may damage the sensitive hair cells in the ears, leading to sensorineural hearing loss.

Several studies have found a connection between sleep apnea and hearing loss. One study of 120 patients at a sleep disorders clinic found that moderate to severe sleep apnea negatively affected hearing functions, with more severe apnea impacting all hearing functions. Another study of nearly 14,000 people found that hearing impairment was more common in those with severe sleep apnea, higher body mass index, and snoring. A smaller study also linked low oxygen levels in people with severe sleep apnea to a higher likelihood of hearing impairment.

While the exact mechanism is not fully understood, the reduced blood flow to the inner ear due to apnea may cause cochlea inflammation over time, contributing to hearing loss. Additionally, sleep apnea can lead to exhaustion and increase the risk of heart disease, further impacting overall health.

Hearing loss and sleep quality research

Although the connection between sleep and hearing loss is not entirely understood, scientists believe that the two are linked. Hearing loss can cause sleep problems, and sleep problems can cause hearing loss.

Hearing Loss Leading to Sleep Problems

According to studies, two-thirds of patients with hearing loss have insomnia. Psychological distress and mood disorders are thought to be contributing factors to sleep loss. Tinnitus, a symptom of hearing loss, can also make it difficult to fall asleep.

Sleep Problems Leading to Hearing Loss

Obstructive sleep apnea, which causes a person to repeatedly stop breathing during sleep, has been linked to hearing loss. Sleep apnea reduces blood flow to the inner ear, which can lead to cochlea inflammation and hearing loss over time. Sleep deprivation has also been linked to reduced brain function, especially central auditory processing, which is essential for distinguishing between sounds.

Hearing While Sleeping

Research has shown that we can, in fact, hear while we sleep. Our brains continue to process sounds, and we may even be able to learn new things during the first two stages of sleep. However, once we enter deep sleep, we stop processing external sounds, and our brains begin to rest.

Improving Sleep Quality

Hearing aids have been shown to improve sleep quality for people with hearing loss. While hearing aids are typically removed before bed, wearing them during the day can help improve sleep at night. Additionally, achieving a regular sleep goal of 7-9 hours each night is recommended to protect your hearing.

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