Sleep is known to be central to various physiological and mental processes, including the consolidation of memories, supporting various cognitive functions, helping to clear the brain of neurotoxins, balancing hormones, and promoting cardiovascular health. Some recent neuroscience studies also suggest that sleep disorders, such as insomnia, periodic limb movement disorder, and sleep apnea, could be linked to hearing loss.

The WHO estimates that 1 in 3 people worldwide suffer from sleep disorders at some point in their lives. Understanding the impact of these disorders on other aspects of human experience is thus of the utmost importance, as it could inform the development of new interventions aimed at improving people's sleep patterns, as well as their health and quality of life.

While the link between sleep disorders and hearing loss has been extensively investigated, the extent to which one influences the other remains poorly understood. Some studies have proposed that hearing loss makes it harder for people to sleep well, while others suggest that sleep disorders can worsen auditory health.

Researchers at Air Force Medical University in China recently reviewed previous literature focusing on this topic, with the aim of painting a clearer picture of the relationship between sleep disorders and hearing loss. Their paper, published in Neuroscience, pinpoints some of the key biological mechanisms underpinning both disrupted sleep patterns and a decline in auditory health while also offering insight that could guide the development of new treatments for sleep disorders.

"The intricate relationship between sleep disorders and hearing loss emerges as a burgeoning field of scholarly inquiry," Peng Zhang, Xiaogang An, and their colleagues wrote in their paper. "Numerous studies have illuminated a potential correlation between the two, affecting the quality of life and overall health of individuals.

"Hearing loss, or auditory impairment, serves as a critical indicator of physiological dysfunction, casting a pall over the daily existence and professional endeavours of those affected, potentially leading to irreversible deafness if left untreated. Sleep disorders may cause physical and psychological changes that further affect hearing, while auditory dysfunction may detrimentally impact sleep experienced by individuals."

The review of previous studies carried out by this team of researchers suggests that different stages of sleep can influence auditory perception in distinct ways. For instance, people's ability to process sounds appears to be significantly stronger during non-rapid eye movement (NREM) sleep than during rapid eye movement (REM) sleep.

Past research also showed that hearing loss can adversely impact the quality of sleep among affected individuals. This could be because people experiencing hearing loss are often more sensitive to background noise, and this can make it harder for them to fall asleep or prompt them to wake up more often during the night.

On the other hand, other studies showed that sleep deprivation can increase the risk of auditory impairments later in life. While the mechanisms underlying this relationship are still poorly understood, in some cases, successfully treating sleep disorders could also promote better auditory health.

"Although certain studies have failed to find a direct link between sleep duration and hearing loss, it is evident that sleep-related issues do increase the risk of hearing loss," wrote Zhang, An, and their colleagues.

"Thus, understanding the relationship between sleep disorders and hearing loss, alongside the underlying mechanisms, will help establish interventions aimed at enhancing sleep quality and safeguarding auditory health. This systematic review endeavours to elucidate the correlation between sleep disorders and hearing loss, offering valuable insights and guidance for future basic research and clinical applications."

The review paper by this team of researchers summarises some of the most notable findings gathered over the past decades, outlining the robust correlation between sleep disruptions and a decline in hearing.

In the future, this study could guide further targeted investigations aimed at better understanding the neural and biological mechanisms linking these two seemingly unrelated experiences, which could potentially help to devise new personalised treatments for sleep disorders or initiatives aimed at preventing or mitigating hearing loss.