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A recent study has found that there could be a relationship between age-related hearing loss and Alzheimer’s disease.

The University of Western Australia recently released a study suggesting that impaired auditory function may be a valuable marker of preclinical stages of Alzheimer’s Disease (AD).

As the baby boomer population approaches seniority, the prevalence of dementia has increased dramatically, with doctors estimating that 57 million people worldwide are currently diagnosed with dementia. Without any significant breakthroughs, that number is expected to double every 20 years, potentially reaching 150 million cases by 2050.

Between 60-80 per cent of all dementia cases are due to AD neuropathology, defined by a loss of episodic memory and impaired cognitive function combined with the presence of biomarkers of AD. Early neurodegenerative symptoms can appear anywhere from 10 to 20 years before clinical symptoms.

The National Institute on Aging-Alzheimer’s Association (NIA-AA) group has suggested a concept that subdivides the course of AD into three subsequent stages.

The first stage relates to the pre-clinical stage of AD, referred to as subjective cognitive decline (SCD), effecting between 25 – 50 per cent of adults 65 years and above. The second stage is prodromal – or mild cognitive impairment (MCI) – that shows early clinical symptoms of dementia, effecting approximately 16 per cent of adults over 70 years of age. The third and final stage is onset dementia, characterised by the presence of dementia syndrome.

SCD and MCI stages could potentially present a target population for AD intervention by investigating and understanding the connection between AD and associated health conditions such as the most prevalent health condition affecting older adults: age-related hearing loss (ARHL).

ARHL is characterised by bilateral, progressive, high-frequency deterioration of hearing sensitivity associated with ageing, effecting close to a third of the population over 65.

According to the paper, hearing loss is suggested to be one of the modifiable risk factors for dementia, accounting for up to eight per cent of all dementia cases.

Even at mild levels, evidence indicates that hearing loss increases the long-term risk of cognitive decline and incidentally dementia. Whether this is due to an increase in mitochondrial dysfunction, inflammation or social isolation and depression due to auditory and cognitive deterioration, the answer is unclear.

Research lead Dr Jayakody says that evidence suggests that “early identification and treatment of auditory impairment could delay or prevent neurodegenerative changes due to altered sensory input and slow progression of structural changes at later stages of cognitive decline.”

Further research and, in turn, understanding the relationship between hearing loss and dementia will not only provide valuable insights into detecting early development of cognitive decline but could potentially be used as a catalyst in effective treatment interventions.