Is poor sleep causing your hearing loss?

After a busy week, many of us look forward to a lie-in at the weekend. But could those extra hours of sleep help protect your hearing? A new study suggests they might.

The research from Korea, reported in the medical journal Annals of Epidemiology, examined the sleeping habits of almost 7,000 men and women over 40 who filled in a questionnaire asking what time they went to bed and woke up on weekdays and weekends.

It found that people in their 40s, 50s and early 60s who got an hour or more extra sleep at weekends were significantly less likely to experience age-related hearing loss (presbycusis), even after factoring in other health and lifestyle habits. 

Why might this be?

“It’s an emerging area of research,” says audiologist Franki Oliver, audiology manager at the RNID. “We know that the cochlea, the small organ in your inner ear responsible for hearing, is extremely sensitive to blood flow and oxygen levels.”

The cochlea – about the size of a pea – is filled with tiny sensory hair cells and is supplied by fine blood vessels. If blood flow is restricted due to inflammation, stress, or other health issues, these fragile cells can become damaged. And once gone, unlike other cells in the body, they don’t regenerate – making hearing loss permanent. 

However, Oliver cautions: “This study shows a correlation – it’s impossible to untangle whether there’s actually a causal link at this stage, so further research is needed.”

 How could sleep be linked to hearing loss? 

Studies suggest that sleep is not only important for the health of our heart and blood vessels and but also for our hearing.

Why? Because good circulation is vital for the health of the inner ear. If blood flow is restricted – by inflammation or oxidative stress, in which rogue molecules that damage cells build up in the body – this can lead to cochlear damage and hearing impairment. 

We already know from previous studies that how we sleep – when and how long for – can influence our risk of heart and circulatory disease and conditions such as type 2 diabetes. Having a lie-in at the weekend seems to have a protective effect.

“Weekend catch-up sleep has been suggested to be potentially restorative physiologically,” says Dr Helen Nuttall, principal investigator at the Neuroscience of Speech and Action Laboratory, University of Lancaster, who was not involved in the study. “Suggested mechanisms include reduced inflammation, support for cardiovascular function, and enhanced cellular repair.

“Additionally sleep disturbances, such as short sleep duration and insomnia, are associated with negative cardiovascular consequences that increase the risk for hearing loss.”

Could better sleep really protect our hearing? 

Dr Nuttall believes sleep could be one of several potentially important lifestyle factors that could help keep our auditory system healthy. 

“While many people think hearing loss is an inevitable consequence of ageing, this may not be the case,” she says.

“Age in itself may be relatively unimportant in the decline in hearing experience by many – but not everyone – with the passing years.

“In fact so-called age-related hearing loss may reflect a constellation of lifestyle, health, and environmental factors that have built up over time, meaning there is a real opportunity to prevent, not just manage, hearing loss.”

Which type of sleep is most important for hearing? 

The Korean study didn’t say but as Dr Nuttall observes: “Deep sleep is the most restorative sleep stage, so if weekend catch-up sleep is indeed physiologically restorative it may involve more deep sleep. These suggested restorative mechanisms could all – in theory at least – benefit cochlear function to support hearing.”

A clue could come from tinnitus research analysing brainwave patterns during sleep.   

“In animal studies, those with signs of tinnitus actually sleep more and most of this extra sleep happens during non-REM (non-dreaming) sleep, suggesting this type of sleep may be important in how the brain tries to manage or recover from tinnitus,” says Victoria Bajo Lorenzana, associate professor of Neuroscience at the University of Oxford, who co-led the research.  

Who benefits most from a weekend lie-in? 

The study found protective effects mainly in men and those aged 40 to 64 years.

In men, irregular bedtimes and lack of weekend catch-up sleep were linked to greater risk of hearing loss, while in women, extra weekend shut-eye seemed only to protect against milder hearing decline.

Disappointingly, the same benefits weren’t evident in the over-65s. 

Does sleep duration matter?

This research didn’t find any link between total sleep time and hearing loss. But others suggest that both too little and too much sleep may be harmful to hearing.

A Japanese study found that sleeping more than eight hours was associated with a higher risk of hearing loss. Another from China found too little sleep (less than four or five hours) and too much (more than eight hours) to be linked to hearing problems.

And in the US, research showed that those sleeping more than eight hours performed worse on tasks involving hearing speech in noisy settings.

What else can cause hearing loss as we age? 

 “More than half of the over-55s experience some hearing loss, rising to more than four fifths in the over-70s,” says Oliver.

“We don’t fully understand why but it’s thought to be a result of gradual wear and tear often compounded by a lifetime of sound exposure.”

• Noise – from loud music, machinery, or a sudden blast of sound – is the second leading cause of hearing loss after age-related/wear and tear. It’s a result of stress to those fine sensory hair cells inside the cochlea. “And because both noise-related and age-related damage affect similar areas it can be hard to distinguish in hearing tests,” she adds.
  
  How safe a sound is depends on its loudness as well as how long and how often you’re exposed to it.
  
  “We generally consider that 80 decibels for eight hours over the course of a day is safe,” says Oliver. Over-exposure to sounds at or above 85 decibels (equivalent to a food blender) can damage hearing in a surprisingly short time.
  
  “For example, exposure to 100 decibels – about the level of a nightclub or festival gig – can damage hearing after just 15 minutes so always protect your ears,” she adds.

• Some medications, including certain chemotherapy drugs and antibiotics are also ototoxic, meaning they can damage hearing. 
• High doses of something as common as aspirin have also been linked to hearing issues. Research suggests that more than 1.95g of aspirin a day (around six and a half 300mg tablets) can be detrimental to hearing. The good news is hearing is usually restored once you stop taking aspirin and there’s no evidence that normal doses of aspirin are linked with hearing loss. 
• Infections – whether bacterial, viral or fungal – can also damage the ear at any age. 
• Temporary hearing loss can stem from wax build up, especially in hearing aid users, swimmer’s ear, or changes in pressure from flying.  

What if you suddenly lose hearing? 

“Sudden hearing loss is rare but serious,” warns Oliver.

“If you wake up unable to hear it could be due to viral infection or restricted blood flow. But if treated within 48 to 72 hours – typically with steroids – there’s a chance hearing can be restored. Seek medical help immediately.”