Effectiveness of Kurtosis-Adjusted Cumulative Noise Exposure in Assessing Occupational Hearing Loss Associated With Complex Noise

Abstract

Objectives: Occupational noise-induced hearing loss (NIHL) is one of the most prevalent occupational diseases worldwide. Few studies have been reported on applying kurtosis-adjusted noise energy (e.g., kurtosis-adjusted cumulative noise exposure, CNE-K) as a joint indicator for assessing NIHL. This study aimed to analyze the effectiveness of CNE-K in assessing occupational hearing loss associated with complex noise in typical manufacturing industries.Design: A cross-sectional survey of 1404 Chinese manufacturing workers from typical manufacturing industries was conducted. General demographic characteristics, noise exposure data, and noise-induced permanent threshold shifts (NIPTS) at 3, 4, and 6 kHz (NIPTS 346 ) were collected and analyzed. The role of kurtosis in high-frequency noiseinduced hearing loss (HFNIHL) was also analyzed. The degree of overlap of the two logistic curves (i.e., between complex noise CNE-K and HFNIHL%, and between Gaussian noise CNE and HFNIHL%) was used to evaluate the effectiveness of CNE-K, using a stratified analysis based on age, sex, industry, or job type. Results:The binary logistic regression analysis showed that in addition to age, sex, exposure duration, and Eight-hour Continuous Equivalent A-weighted Sound Pressure Level (L Aeq,8h ), kurtosis was a key factor influencing HFNIHL% in workers (odds ratio = 1.18, p < 0.05), and its odds ratio increased with an increase in kurtosis value. Multiple linear regression analysis demonstrated that the contribution of kurtosis to NIPTS 346 was second to L Aeq,8h . Complex noise led to a higher risk of NIHL than Gaussian noise at frequencies of 3, 4, 6, and 8 kHz after adjusting for age, sex, and CNE (p < 0.05). As kurtosis increased, the notch in the audiogram became deeper, and the frequency at which the notch began to deepen shifted from 3 to 1 kHz. The logistic curve between complex noise CNE-K and HFNIHL% nearly overlapped with that between Gaussian noise CNE and HFNIHL%, and the average difference in HFNIHL% between the two curves decreased from 8.1 to 0.4%. Moreover, the decrease of average difference in HFNIHL% between the two logistic curves was evident in several subgroups, such as male workers, aged <30 and 30 to 50 years, furniture and woodworking industries and gunning and nailing job types with relatively high kurtosis values.Conclusions: Kurtosis, as an indirect metric of noise temporal structure, was an important risk factor for occupational NIHL. Kurtosis-adjusted CNE metric could be more effective than CNE alone in assessing occupational hearing loss risk associated with complex noise.

The role of kurtosis and kurtosis-adjusted energy metric in occupational noise-induced hearing loss among metal manufacturing workers

“…Moreover, logistic regression analysis suggested that after adjusting for age, sex, and CNE, kurtosis greater than 10 led to a higher risk for NIHL than that less than 10 since the OR value was greater than 2 at the frequency of 3, 4, 6, or 8 kHz, which suggested that complex noise was more harmful to the auditory system than Gaussian noise; There was an independent effect of kurtosis on NIHL development after controlling for CNE and age. These results agreed with previous studies ( 15 , 17 , 24 , 27 ). For example, Zhao et al found that workers exposed to complex noise had a higher risk of NIHL than those exposed to Gaussian noise (OR = 1.806) ( 24 ).…”

“…The possible reason for the ‘V’ shape notching only in males may be that the male workers suffered more significant HFNIHL% caused by complex noise than females ( 33 ), and they were more likely exposed to complex noise environments such as punching, stamping, metalworking, woodworking, and nail gunning ( 34 ). Besides, one study of 1,404 Chinese manufacturing workers reported similar findings that the V- or U-shaped notch phenotypes of NIPTS broadens and deepens with increasing kurtosis, even widened to 1–8 kHz when β > 100 ( 27 ). Notably, the kurtosis-associated notch initially occurred at high frequencies and reached the notching bottom at 4 or 6 kHz, with the notch range of 3–8 kHz when β < 10, indicating that noise exposure led to greater hearing loss at high frequencies.…”

“…Because the worker population in this study was rigorously screened, the pure-tone hearing threshold levels (HTLs) were adjusted according to sex and age by following Annex A, Table A.3, of ISO 1999:2013. In this study, high-frequency NIHL (HFNIHL) was diagnosed as one or more adjusted HTLs, in either ear, at 3, 4, or 6 kHz equal to or higher than 30 dB based on an extensive body of prior research ( 14 , 15 , 21 , 22 , 26 , 27 ). The analysis focused on the noise-sensitive frequency range of 3, 4, and 6 kHz because the noise-induced hearing loss from continuous noise occurs predominantly in this range initially ( 28 ).…”

“…The differences in NIPTS 346 and HFNIHL% between complex noise exposure workers and Gaussian noise exposure workers before and after CNE adjustment by kurtosis were evaluated using paired sample t-test. CNE was further divided into eight subgroups based on the cut-off points of 90, 95, 100, 105, 110, 115, and 120 as shown in our previous studies ( 21 , 22 , 27 ). Herein, the dose–response relationship of Gaussian noise served as a baseline to determine whether adj-CNE could effectively assess NIHL.…”