The relationship between Parkinson’s disease and hearing loss

March 9, 2016 by Sarah Fredj

Parkingson

Studies suggest that elderly people suffering from Parkinson’s disease are also more at risk of experiencing hearing loss.

What is Parkinson’s disease?

Parkinson’s is a neurodegenerative disease that mainly affects movement. It’s caused by cell death in an area of the brain called the “substantia nigra.” The affected cells produce dopamine, a chemical that functions as a neurotransmitter, sending signals between the brain cells involved in movement. The significant decrease in dopamine levels causes the symptoms of Parkinson’s to appear. By the time Parkinson’s is diagnosed, it’s estimated that approximately 80% of dopamine-producing cells have stopped functioning.

The disease is more frequent in elderly people, affecting approximately 1% of those aged 65 and over and 2% of those aged 70 and over. In Canada, some 100,000 people have the disease, including 25,000 in Quebec alone.

A number of symptoms characterize Parkinson’s, but resting tremor is certainly the most indicative, followed by absence/loss and slowness of movement (akinesia and bradykinesia), muscular rigidity, and postural instability.

Is there a relationship between Parkinson’s and hearing loss?

A recent study conducted in Taiwan shows that elderly people with Parkinson’s are 1.5 times more likely to have hearing loss.

To carry out the study, Taiwanese researchers (Lai et al., 2014) created two groups. The first comprised 5,000 patients aged 65 and over diagnosed with hearing loss between 2000 and 2010, while the second comprised 19,900 randomly selected people with normal hearing.

By comparing the proportion of people in each group that eventually developed Parkinson’s, the researchers determined that the incidence of the disease was 1.5 times greater in the group with hearing loss, and were also able to confirm a positive correlation between Parkinson’s and hearing loss in elderly people.

Decrease in dopamine = hearing loss?

Another team of researchers (Vitale et al., 2012) has proven that dopamine could have a protective effect on the hearing organ: the cochlea. As Parkinson’s is caused by a decrease in dopamine and a direct correlation has been found between hearing loss and Parkinson’s disease, researchers hypothesized that inadequate levels of dopamine, combined with age, could damage the cochlea.

Even if the results of the research cited suggest this is true, it is too soon to state with certainty that hearing loss is a nonmotor symptom. So we’ll keep our ears to the ground while awaiting the results of further studies!

References:
– Lai, S. W., et al. (2014). “Hearing loss may be a non‐motor feature of Parkinson’s disease in older people in Taiwan.” European Journal of Neurology, 21(5), 752–757.
– Vitale, C., et al. (2012). “Hearing impairment in Parkinson’s disease: Expanding the nonmotor phenotype.” Movement Disorders, 27(12), 1530–1535.
-Pisani, V., et al. (2015). “An investigation of hearing impairment in de-novo Parkinson’s disease patients: A preliminary study.” Parkinsonism & Related Disorders, 21(8), 987–991.
– Parkinson Québec (2015). “Qu’est-ce que la maladie?” Website parkinsonquebec.ca viewed on 2015-10-22.

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