Although Parkinson’s disease primarily presents with motor symptoms, other non-motor symptoms, such as depression, anxiety, and olfactory impairment, have begun to be recognized as important parts of the condition’s presentation. In fact, these non-motor symptoms contribute significantly to the quality-of-life impacts in patients with Parkinson’s disease. Moreover, non-motor symptoms may predate motor symptoms, making them important indicators of risk for Parkinson’s. For example, Rapid Eye Movement Sleep Behavior Disorder converts to Parkinson’s disease in 44% of patients.
Hearing loss, often considered a part of normal aging, has been identified as a potential risk factor for dementia. Some research has even shown that hearing loss doubles the risk of developing dementia symptoms. Although unclear, there is likely a common physiological cause of neuronal degeneration in the auditory system and the cortex, which causes hearing loss and dementia, respectively. Some evidence suggests the same may be true in Parkinson’s disease. Mitochondrial dysfunction and the aggregation of alpha-synuclein, for example, are both implicated in hearing loss and Parkinson’s, suggesting a common pathology.
Research has shown that clinically diagnosed hearing loss was associated with a significantly increased risk of receiving a Parkinson’s diagnosis within 5 years. However, another study showed that self-reported hearing loss was not associated with an increased risk of Parkinson’s over a 10-year follow-up period, despite some noted study design faults of relying on self-reports of hearing loss versus bona fide clinically diagnosed hearing loss.
A large prospective cohort database study recently published in the journal Parkinsonism and Related Disorders aimed to help better elucidate the link between hearing loss and Parkinson’s, potentially clarifying the inconsistencies in existing research. The study aimed to examine the relationship between a speech-in-noise test, which measures hearing loss, and the incidence of Parkinson’s in the UK Biobank database.
Data were provided by 503,325 participants aged 40-69, all of whom were assessed via questionnaire for demographic, health, and lifestyle data, and completed the Digit Triplet Test (DTT) for hearing. The DTT presents 15 sets of monosyllabic digits with varying levels of background noise, estimating the ability of study participants to recognize the correct tones and the speed with which participants could recognize the correct tones. This measure helped identify patients with clinically significant hearing loss. With that in mind, the primary outcome was a diagnosis of probable Parkinson’s, defined as a composite of self-reported and hospital-related clinical diagnoses. Participants who went on to develop dementia were excluded to improve interpretability of the data.
The study sample included 159,395 eligible participants (54% female) from the UK Biobank cohort. Over a median follow up of 14.24 (SD=0.58) years, 801 cases of incident Parkinson’s were reported (5%). Those who were diagnosed with Parkinson’s were significantly more likely to be older, male, less highly educated, and report using a hearing corrective device, a key indicator of hearing issues.
After adjusting for age, sex, and education level, the risk of incident Parkinson’s was 1.57 (95% CI, 1.018, 2.435; P=0.041) per 10 dB increase in SRT, meaning that people are at 57% greater risk for Parkinson’s as hearing loss becomes more severe. Although there are limitations to this analysis, it does provide compelling evidence of the severity of hearing loss and the risk of incident Parkinson’s.
“Critically, we observed that after adjustment for sex, age, and educational attainment, hearing impairment was independently associated with incident Parkinson’s, and this finding was robust to multiple sensitivity analyses,” state the authors. They additionally note that some participants diagnosed with Parkinson’s may instead have a parkinsonism which requires a differential diagnosis, sometimes confirmed with biomarker testing. “Situating the present findings within the current partially inconsistent body of literature may provide further insight to the mechanism by which hearing impairment and Parkinson’s are related.”
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References:
Readman MR, Wang Y, Wan F, et al. Speech-in-noise hearing impairment is associated with increased risk of Parkinson’s: A UK biobank analysis. Parkinsonism Relat Disord. 2025;131(107219). doi:10.1016/j.parkreldis.2024.107219
Simonet C, Bestwick J, Jitlal M, et al. Assessment of risk factors and early presentations of Parkinson disease in primary care in a diverse UK population. JAMA Neurol. 2022;79(4):359–369. doi:10.1001/jamaneurol.2022.0003
Readman MR, Wan F, Fairman I, Linkenauger SA, Crawford TJ, Plack CJ. Is hearing loss a risk factor for idiopathic Parkinson’s disease? An English longitudinal study of ageing analysis. Brain Sci. 2023;13(8):1196. doi: 10.3390/brainsci13081196
