A Simple Nomogram for Predicting Extended High-Frequency Hearing Loss in Pilots Despite Normal Audiometry: A Retrospective Study.

Abstract

Background: The extended high-frequency (EHF; 0.9-16 kHz) region is sensitive to noise exposure and can indicate early noise-induced hearing loss. EHF hearing loss (EHFHL; >20 dB HL for EHF averages) may affect pilots' noise perception, impacting communication and response in flight. Early identification and monitoring of EHFHL are crucial for pilots' hearing health and flight safety. However, EHF is not included in routine medical assessments for pilots in China. This study aimed to develop a nomogram to predict EHFHL in pilots with normal audiograms (≤20 dB HL at each standard frequency), providing an early intervention tool.

Methods: A total of 1091 pilots were randomly assigned to the training set (763) and validation set (328). Set characteristics were compared using univariate analysis. In the training set, least absolute shrinkage and selection operator regression identified key predictors, followed by multivariable binary logistic regression to construct a nomogram. The nomogram's performance was evaluated in both sets, assessing calibration, discrimination and clinical utility.

Results: The nomogram incorporated four factors as follows: left-ear high-frequency audiometry threshold averages (HFAs: 3, 4, 6 and 8 kHz; odds ratio [OR] = 1.144; 95% confidence interval [CI] = 1.083-1.210), right-ear HFAs (OR = 1.186, 95% CI = 1.115-1.263), flight time (OR = 1.001, 95% CI = 1-1.001) and triglyceride (OR = 1.393, 95% CI = 1.038-1.885). The model's area under the curve was 0.819 (95% CI = 0.790-0.850) and 0.771 (95% CI = 0.712-0.830) during validation. The predictive model was well calibrated (Hosmer-Lemeshow test, χ2  =  10.77; P = 0.292). Decision curve analysis showed a net benefit for the training set between 4% and 88%, with similar benefits observed for the validation set from 12% to 100%.

Conclusion: This study developed and validated the first prediction model for EHFHL in Chinese pilots, demonstrating its reliability and clinical utility. The findings support early detection and personalised monitoring, with potential applications in hearing protection strategies and flight safety.