Associations Between Noise Exposure Level, Noise Kurtosis, and Distortion Product Otoacoustic Emissions in Young Workers With Normal Hearing.

The study measured participants at one time point, so it cannot show that noise exposure caused the lower DPOAE levels. DPOAE testing was done only once, so repeat testing would make the results more stable. All participants had normal hearing thresholds and were aged 18 to 42 years, so the results may not apply to older workers or people with hearing loss. The study did not include factors such as education, smoking, and cardiovascular risk factors that can affect DPOAEs. Hearing protection use was recorded by questionnaire and observation, but fit, training, and actual protection were not measured. Many frequencies were tested, and some differences were based on multiple comparisons; the authors used a correction, but the findings still need confirmation. Exclusions reduced 737 recruited to 549 analysed, mainly because of age, hearing thresholds, or missing tests.

Funding came from a National Institute on Deafness and Other Communication Disorders grant, Grant No. 1R01DC015990, plus Zhejiang Health Commission projects, a Zhejiang CDC talent project, and Zhejiang Chinese Medical University. The authors declared no conflicts of interest.

Do not read the lower DPOAE levels as proof that workplace noise caused hearing loss or that these workers have hearing loss. The study was cross-sectional and all participants had normal hearing thresholds, so it reports an association with a cochlear response test, not cause or hearing loss.