A hearing impairment developed with age could increase risk of Parkinson's disease by up to 57 per cent and thus, serve as an early warning sign, according to a study.

While hearing loss has been associated with cognitive decline and considered a risk factor for dementia, this study, published in the journal Parkinsonism and Related Disorders, is one of the first to examine how hearing impairment could increase the risk of Parkinson’s disease.

Researchers, led by Lancaster University in the UK, said that it is still unclear whether hearing loss is correlated with or causes the neurodegenerative condition, which affects movement and coordination and can also cause tremors or shaking.

Proposing potential mechanisms, the team suggested that depleted dopamine levels could play a role, as previous studies have found low dopamine levels in both individuals with hearing loss and patients with Parkinson’s disease. Dopamine is known to be important for processing sound.

"It is increasingly clear that hearing loss is not an isolated condition but is associated with several other disorders. Understanding these links is vital if we are to provide effective patient care, improving independence and quality of life for the individuals concerned," said Christopher Plack, a professor in the Department of Psychology at Lancaster University.

For the study, the researchers analysed data from nearly 1.6 lakh individuals in the UK Biobank dataset. The participants had previously undergone hearing tests that measured how well they could detect speech in a noisy environment and had no history of Parkinson’s disease at the time of the assessment.

Over the follow-up period of more than 14 years, 810 participants were diagnosed with the neurodegenerative condition.

"Parkinson's risk increased by 57 per cent for every 10 dB (decibels) increase in hearing impairment," the authors wrote.

Lead researcher Megan Readman, a postdoctoral research fellow at Lancaster University's Department of Psychology, said, "These findings are incredibly important; first, this is one of the first studies to look at how hearing impairments may increase the risk for Parkinson's or serve as an early warning sign." Additionally, by identifying factors that might contribute to the onset of Parkinson's disease, such as hearing impairment, the findings could pave the way for prevention and care.

"Our findings suggest that hearing impairment is intricately related to Parkinson's disease and underscore the potential benefits of addressing auditory function in Parkinson's diagnosis and follow-up care," Readman said.

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