Hearing Loss Associated With Parkinson Disease Diagnosis, Large-Scale Study Shows

Lee E. Neilson, MD

Recently published data using electronic health records for more than 3 million US veterans revealed that hearing loss was an independent risk factor for later development of Parkinson disease (PD), even after adjusting for competing risk of death, age, head trauma, frailty, and established prodromal disorders. Investigators concluded that hearing screening and hearing intervention are low-cost, low-risk measures that may influence the later development of synucleinopathy and could be the most important modifiable risk factor for both dementia in midlife and PD.¹

Published in JAMA Neurology, the analysis included electronic health record data from the US Department of Veterans Affairs for veterans who had an audiogram (n = 3,596,365) from January 1999 to December 2022. Of those included, 20.8% (n = 750,010) had normal hearing (<20 dB) at the time of audiometry examination. The cohort, which mostly comprised middle-aged White males, also included smaller populations of individuals who identified as Asian (0.9%; n = 33,242), Black (11.3%; n = 407,572), and Native American (0.6%; n = 25,026).

Led by the Lee E. Neilson, MD, a neurologist at the Portland VA Medical Center, the cohort was followed up for a mean of 7.6 (SD, 4.4) years. During that time, the incidence rate for PD ranged from 3.69 to 11.6 per 10,000 person-years and for death, 103 to 1140 per 10,000 person-years, across hearing loss groups. All told, veterans with mild hearing loss had a higher cumulative incidence of PD compared to those with normal hearing at 5, 10, 15, and 20 years after the first audiogram, with additional PD cases per 10,000 people ranging from 2.0 (95% CI, 0.9-3.1) at 5 years to 9.5 (95% CI, 7.7-11.4) at 20 years.

In the study, investigators found that hearing loss of any severity was associated with an increased risk of PD at 10 years, with a hazard ratio of 1.26 (95% CI, 1.2-1.32; P <.001) compared with normal hearing. In addition, hearing loss in the absence of prodromal PD disorders, traumatic brain injury (TBI), or tinnitus was consistently associated with the risk of PD that increased with hearing loss severity and time.

Results showed that prodromal PD disorders alone and TBI alone in the absence of hearing loss were associated with the increased risk of PD whereas this was not seen for tinnitus without hearing loss. Specifically, the combination of hearing loss and prodromal PD disorders accounted for up to 21.7 (95% CI, 6.7-36.6) additional cases of PD above what is expected from either condition alone. Similar dose- and time-dependent trends were observed for the interactions as for the main effects.

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In an exploratory analysis, results showed that administration of hearing aids within 2 years after an initial audiogram led to a significant reduction in incident PD as early as 1 year in. This was true for both all individuals and only those with impaired hearing. This estimate translated to 462 people needing to be treated with a hearing aid after an abnormal audiogram to protect 1 person from developing PD 10 years later.

"While our data provide strong evidence that hearing aid administration reduces PD risk on a population level, the pre- sent methods did not allow us to assess hearing aid adherence or physical, cognitive, or other social factors influencing the prescription probability or decision to wear a hearing aid, which may be moderators of the expected benefit," Neilson et al wrote.¹ "In particular, the possibility remains that the individuals who receive hearing aids under current practice policy tend to be those most expected to benefit from them, and it is unknown whether this benefit would extend to any potential user if dispensation were expanded more broadly. Further prospective studies assessing individual abilities to understand speech in the absence of pure tone identification are also warranted."

The study had several limitations. The cohort, consisting exclusively of US veterans who are predominantly White and male, may limit the generalizability of findings, though this demographic represents a high-risk group. While the representation of racial and ethnic minority groups is relatively small, the absolute numbers surpass those in similar studies, such as one evaluating a UK population. Potential confounders, such as ototoxic drug exposure, were not examined, and while a strong association between hearing loss and PD was observed, causality and mechanisms remain unclear.

REFERENCE
1. Neilson LE, Reavis KM, Wiedrick J, et al. Hearing loss, incident Parkinson disease, and treatment with hearing aids. JAMA Neurol. Published online October 21, 2024. doi:10.1001/jamaneurol.2024.3568