Influence of well-known risk factors for hearing loss in a longitudinal twin study

Quantitative levels of noise exposure and 20-year hearing decline: findings from a prospective cohort study (the HUNT Study)

OBJECTIVE

We aimed to assess the association between occupational noise exposure and long-term hearing decline.

DESIGN

This prospective cohort study used linear regression to investigate the association between occupational noise exposure and 20-year hearing decline, adjusted for important confounders.

STUDY SAMPLE

The Norwegian cohort (N = 4,448) participated in two population-based health studies with pure-tone audiometry; HUNT2 1996-1998 and HUNT4 2017-2019. Exposure assessments included a quantitative job exposure matrix (JEM) and questionnaires.

RESULTS

The participants (40.2% men, 20-39 years at baseline) had a mean 20-year decline (3-6 kHz) of 11.3 ± 9.8 decibels (dB). There was a positive association between 20-year logarithmic average noise level (JEM-based, LEX,20y) and 20-year hearing decline among men. Compared with no exposure ≥80 dB during follow-up, minimum 5 years of exposure ≥85 dB (JEM-based) predicted 2.6 dB (95% CI: 0.2-5.0) larger 20-year decline for workers aged 30-39 years at baseline, and -0.2 dB (95% CI: -2.2 to 1.7) for workers aged 20-29 years. Combining JEM information with self-reported noise exposure data resulted in stronger associations.

CONCLUSION

This large longitudinal study shows an association between JEM-based noise exposure level and increased 20-year hearing decline among men. Contrary to expectations, the associations were weaker among younger workers, which might reflect a latency period.

Risk of Noise-Induced Hearing Loss for Orthopaedic Surgeons

BACKGROUND

Noise-induced hearing loss (NIHL) affects the ability of an individual to communicate and can negatively impact quality of life. The risk to orthopaedic surgeons of developing NIHL as a result of occupational exposures in the operating room (OR) is currently unknown. Hearing protection is recommended for levels of >85 decibels (dB), irrespective of length of exposure. The primary goal of the present study was to determine whether orthopaedic surgeons are exposed to harmful noise levels in the OR that puts them at risk for developing NIHL.

METHODS

A prospective review was conducted with use of intraoperative audio recordings across 6 orthopaedic subspecialties. Recordings were made in ORs prior to the surgical start time to serve as baseline controls. Decibel levels were reported as the maximum dB level (MDL), defined as the highest sound pressure level during the measurement period, and as the time-weighted average (TWA), defined as the average dB level projected over an 8-hour time period. Noise doses were reported as the percentage of maximum allowable daily noise (dose) and as the measured dose projected forward over 8 hours (projected dose).

RESULTS

Three hundred audio recordings were made and analyzed. The average MDL ranged from 96.9 to 102.0 dB, with noise levels for all subspeciality procedures being significantly greater compared with the control recordings (p < 0.001). Overall, MDLs were >85 dB in 84% of cases and >100 dB in 35.0% of cases. The procedure with the highest noise dose was a microdiscectomy, which reached 11.3% of the maximum allowable daily noise and a projected dose of 104.1%. Among subspecialties, adult reconstruction had the highest dose and projected dose per case among subspecialties.

CONCLUSIONS

The present results showed that orthopaedic surgeons are regularly exposed to damaging noise levels (i.e., >85 dB), putting them at risk for permanent hearing loss. Further investigation into measures to mitigate noise exposure in the OR and prevent hearing loss in orthopaedic surgeons should be undertaken.

CLINICAL RELEVANCE

Orthopaedic surgeons are at risk for NIHL as a result of occupational exposures in the OR.

Evaluating Risk of Noise-Induced Hearing Loss in Otologic Surgery

OBJECTIVES

To evaluate risk for noise-induced hearing damage from otologic surgery-related noise exposure, given recent research indicating that noise levels previously believed to be safe and without long-term consequence may result in cochlear synaptopathy with subsequent degeneration of spiral ganglion neurons, degradation of neural transmission in response to suprathreshold acoustic stimuli, and difficulty understanding in background noise.

METHODS

A prospective observational study of surgeon noise exposure during otologic and neurotologic procedures was performed in a tertiary care center. Surgeon noise exposure was recorded in A- and C-weighted decibel scales (dBA, dBC), including average equivalent (LA_eq) and peak (LA_peak, LC_peak) levels and noise dose.

RESULTS

Sound measurements taken at the ear with continuous recording equipment during cadaveric otologic surgery demonstrated LA_eq 80-83 dBA, LA_peaks of 105 dBA, LC_peaks of 127 dBC, with noise doses of 0.9% to 6.7%. Sound level measurements during live surgery translabyrinthine approaches yielded lower LAeq of 72 to 74 dBA and lower noise doses compared with temporal bone lab measurements. Raw sound recordings during live surgery demonstrated narrow band, high frequency, high amplitude spikes between 4 and 12 kHz.

CONCLUSION

Noise exposure to surgeons, staff, and patients in the operating room is acceptable per NIOSH recommendations. Temporal bone lab noise exposures are greater, possibly due to poorly maintained drill systems and lack of noise shielding from microscope bulk, yet are also within NIOSH recommended levels.

Genome-wide association study identifies 7q11.22 and 7q36.3 associated with noise-induced hearing loss among Chinese population

Noise-induced hearing loss (NIHL) seriously affects the life quality of humans and causes huge economic losses to society. To identify novel genetic loci involved in NIHL, we conducted a genome-wide association study (GWAS) for this symptom in Chinese populations. GWAS scan was performed in 89 NIHL subjects (cases) and 209 subjects with normal hearing who have been exposed to a similar noise environment (controls), followed by a replication study consisting of 53 cases and 360 controls. We identified that four candidate pathways were nominally significantly associated with NIHL, including the Erbb, Wnt, hedgehog and intraflagellar transport pathways. In addition, two novel index single-nucleotide polymorphisms, rs35075890 in the intron of AUTS2 gene at 7q11.22 (combined P = 1.3 × 10^-6 ) and rs10081191 in the intron of PTPRN2 gene at 7q36.3 (combined P = 2.1 × 10^-6 ), were significantly associated with NIHL. Furthermore, the expression quantitative trait loci analyses revealed that in brain tissues, the genotypes of rs35075890 are significantly associated with the expression levels of AUTS2, and the genotypes of rs10081191 are significantly associated with the expressions of PTPRN2 and WDR60. In conclusion, our findings highlight two novel loci at 7q11.22 and 7q36.3 conferring susceptibility to NIHL.

Audiometric findings of printing press workers exposed to noise and organic solvents

OBJECTIVE

To determine if exposure to organic solvents and noise is associated with audiometric results among workers from a printing press in Mexico City.

DESIGN

Cross-sectional study.

STUDY SAMPLE

One hundred and seventy-six male workers at a printing press in Mexico City exposed to noise and organic solvents, including xylene, and 103 non-exposed male workers as reference group. Hearing thresholds were assessed with pure-tone audiometry.

RESULTS

Poorer hearing thresholds were observed among printing workers than non-exposed controls, particularly among groups with over 5 years of exposure. Hearing thresholds differences were observed in the frequencies above 500 Hz, especially in 4000 Hz in all exposure groups compared to the reference. Adjusted models for age and previous exposure to noise and organic solvents showed worse hearing thresholds as years of seniority increased -β coefficients (95% CI): ≤5 years: 3.06 dB (0.01, 6.10); >5-10 years: 4.51 dB (1.13, 7.89); >10 years: 4.58 dB (1.20, 7.96). Further analyses showed no interaction between noise and organic solvents on hearing thresholds, considering both current and previous occupational exposures.

CONCLUSION

Exposure to noise levels that were below recommended exposure limits and organic solvents were associated with poorer hearing thresholds than those observed among non-exposed study participants. This suggests that workers exposed to solvents should be included in hearing conservation programmes, even when noise exposures are below 85 dB. If only noise levels were taken into consideration in the risk assessment of this worker population, the risk of hearing effects could have been overlooked.