A large cohort study analyzing electronic health record data from the U.S. Department of Veterans Affairs found that hearing loss is associated with an increased risk of developing Parkinson's disease, with hearing aids potentially reducing this risk. The study, published in JAMA Neurology, examined data from 3,596,365 veterans between January 1, 1999, and December 30, 2022.

The study population was predominantly male (96%) with a mean age of 67 years. Among participants, 750,010 (20.8%) had normal hearing, while 1,080,651 (30.0%) had mild hearing loss, 1,039,785 (28.9%) had moderate hearing loss, 568,296 (15.8%) had moderate to severe hearing loss, and 157,623 (4.3%) had severe to profound hearing loss.

At 10 years after baseline audiogram, researchers observed additional cases of Parkinson's disease (PD) per 10,000 people compared with those with normal hearing:

• Mild hearing loss: 6.1 additional cases (95% CI, 4.5-7.7)
• Moderate hearing loss: 15.8 additional cases (95% CI, 12.8-18.8)
• Moderate to severe hearing loss: 16.2 additional cases (95% CI, 11.9-20.6)
• Severe to profound hearing loss: 12.1 additional cases (95% CI, 4.5-19.6)

When combined with established prodromal conditions, hearing loss was associated with 5.7 (95% CI, 2.2-9.2) additional cases of PD at 10 years compared with either condition alone. The study found that prompt hearing aid dispensation within two years of audiogram was associated with 21.6 fewer cases of PD per 10,000 people (95% CI, 19.5-23.6) at 10 years.

Study limitations include the predominantly White male veteran population and inability to assess hearing aid adherence. The researchers note that additional studies are needed to examine the mechanisms underlying the association between hearing loss and PD.

The study was supported by Veterans Affairs Biomedical Laboratory Research and Development, among other funding sources. One author reported being listed as a co-inventor on a patent involving an ototoxicity monitoring method.