Hearing loss is more than a nuisance - it’s been termed a public health concern, and it affects over 466 million people worldwide.

Article by Larisa Dina who is a researcher finishing her PhD at King’s College London. Larisa is writing exclusively for the Purposeful Group companies of which we are a part, and is an expert on digital health.

What is hearing loss?

There isn’t a single cause behind it: genetics, environmental noise, and increased age are at play. According to the World Health Organization, one in three people over 65 experiences hearing loss severe enough to interfere with daily life.

The impact goes far beyond asking others to repeat themselves. Hearing difficulties can quietly erode social confidence, leading to isolation and reduced engagement in conversations and activities.

At the same time, as people live longer and dementia becomes more common, the scientific community is turning to modifiable risk factors – those we can change to reduce the likelihood of cognitive decline later in life. While it is perhaps intuitive that stress or poor sleep might affect the brain, hearing loss emerged as a surprising, but most important modifiable risk factor by the Lancet commission on dementia prevention, intervention, and care in their 2017, 2020 and 2024 updates.

Hearing loss increases dementia risk

This 2024 study published in JAMA Ortolaryngology analysed electronic health records from half a million Danish adults aged 50 years and above, and found that hearing loss was significantly associated with a 7% increased risk of dementia. Interestingly, they also reported that those with more impairment were at higher risk.

Similar results were reported in this 2023 study from The Lancet of 7,000+ elderly Norwegian adults. Following people over an average period of ~22 years, they found that for every 10 dB worsening in hearing thresholds, the risk of dementia increased by approximately 4%. These results were similar for Alzheimer’s Disease and other types of dementia (non-Alzheimer’s Disease dementias). Importantly, in adults under 85 years (so 70-84 years in this sample), the risk was higher – there was a moderate 12% increased risk associated with 10 dB hearing loss. This association was not found in adults aged 85 years and above, but the authors interpreted this null finding as likely being influenced by dropout from the study, possibly due to survival bias – when only those who live longer remain in the study. Notably, this study shows that hearing loss does not need to be severe to increase risk for dementia – even with an increase of only 10dB, the increase in dementia risk is moderate.

Overall, high quality evidence from long-term studies in large samples shows that hearing loss is associated with an increased risk in dementia, and that this is independent of other health conditions, demographic factors like age and gender, and lifestyle factors.

How is hearing loss associated with dementia?

The short answer is that this is not entirely understood. However, researchers are hard at work trying to understand these mechanisms, and there are some promising clues.

The most widespread framework suggests that hearing loss is associated with (1) changes in the structure and function of the brain – areas of the brain associated with speech perception might shrink, and some of these are the same areas involved in other important processes like remembering and processing information, ; (2) an increase in cognitive demands, as fragmented hearing makes it harder to focus and requires more effort; (3) social isolation, as a result of not being able to participate in conversations – and loneliness is a known risk factor for dementia.

A large study of 100,000+ individuals who contributed brain scans and assessments to the UK Biobank supports this proposed framework. The authors reported that hearing loss is associated with lower brain volume (brain atrophy) in regions that are also known to be implicated in dementia, and steeper decline in cognitive functioning, as assessed using various memory and general cognition tasks. They also found an association with some proteins known to be involved in Alzheimer’s Disease.

What to take away from this piece

Hearing loss is, to an extent, preventable and treatable – hence why we call it a modifiable risk factor. The JAMA Ortolaryngology study mentioned above reported that people with untreated hearing loss (e.g., not using a hearing aid) were at considerably higher risk compared to those who were using hearing aids. This suggests that treating hearing loss can counteract or delay the development or progression of dementia. One mega-study summarising data from 17 individual studies over 30 years found that hearing aids have a beneficial impact on executive functions – these refer to our abilities to remember things, act in a way that is goal-appropriate, make plans and be adaptable. This aligns well with results from another influential study published in the Lancet in 2023, this time with data from adults 70-84 years in the US. Here, researchers recruited adults with untreated hearing loss and randomly assigned them to either receive a hearing aid or receive general health advice. After 3 years, the rate of cognitive decline was not significantly different between the groups. However, interestingly, they found that the subgroup most at risk for cognitive decline within the bigger group receiving hearing aids had half the rate of cognitive decline over three years than people in the control group (receiving general health advice and no hearing aids).

Whilst treatment is incredibly important, prevention remains paramount. A BMJ Global Health study warns that as many as 1.35 billion people around the world could be at risk of hearing loss from unsafe listening habits. However, limiting headphone use and loud entertainment venues is a practice we can all implement to reduce our risk of hearing loss. For headphones, a safe listening volume is no more than 60% of maximum (or below 80dB). You can find more information on safe listening here.

There is no doubt room for more research to be conducted in this area. Nonetheless, the evidence so far is convincing – hearing loss is a strong modifiable risk factor for dementia, and treating it using hearing aids reduces cognitive decline and risk for dementia, at least in those most at risk. Ultimately, prevention remains paramount, and something we can all do through limiting exposure to loud environments and keeping the volume down on our headphones.