Skip to main content

Table 1 Summary of literature on asymmetric NIHL

From: Current insights in noise-induced hearing loss: a literature review of the underlying mechanism, pathophysiology, asymmetry, and management options

First authors & year Design Participants Calculation Methods Asymmetry Criteria Outcomes Additional factors considered
May et al. 1990 [101] Case series 49 dairy farmers 94% male, 6% female mean age 43.5 average farming 29.4 years 0.5,1, 2, 3 kHz (PTA)
3, 4, 6 kHz (HFA)
>20 dB average hearing loss in either ear Left ear is more severely affected in both groups. 37% abnormal PTA, 65% abnormal HFA.
Significant association with years worked and age.
presbycusis, small sample.
Ostri et a1. 1989 [102] Case series 95 orchestral musicians 80 males, 15 females age 22–64 0.125, 0.25, 0.5, 0.75, 1, 1.5, 2, 3, 4, 6, 8 kHz (PTA) >20 dB average hearing loss in either ear 44% of musicians had hearing impairment attributed to occupational noise exposure.
Significant poorer hearing on the left ear found at higher frequencies among violinist.
instrument played, side of orchestral band, previous noise exposure
Cox et a1 1995 [63] Case series 235 soldiers with past weapon noise exposure age 16–55 0.5,1, 2, 3,4, 6 kHz (average single frequency threshold) Interaural difference = asymmetry >10 dB 67% asymmetry at 4 kHz.
Average hearing loss and interaural asymmetry increased with frequency.
handedness, emotional immaturity, motivation for army service, use of ear defenders
Pirila et al. 1992 [109] Cross-sectional study 3487 random people 1640 males, 1847 females 3 age groups (5–10,15–50, >50) 0.125, 0.25,0.5,1, 2, 3, 4, 6, 8 kHz (average single frequency threshold) Interaural difference = asymmetry >0 dB The inferiority of hearing in the left ear at 4 kHz seems to be assiciated with noise damage.
The average interaural difference at 4 kHz was more marked in age 15–50.
shooting history occupational noise exposure
Pirila et al. 1991 [98] Cohort study 28 non-shooting normal HL 10 males, 18 females age 17–29 exposure to broad band noise 88–91 dB for maximum 8 h 4 kHz (average single frequency threshold) determine TTS after noise exposure TTS was greater in the left ear than the right.
Negative correlation between pre-exposure threshold level.
rely on history, samll sample size.
Chung et al. 1983 [95] Audiology Case series 1461WCB claims for NIHL no head injury, no ear surgery age 36–82 2 kHz (average single frequency threshold) >20 dB 4.7% has asymmetry, suggesting damage toward apex. 82.6% has worse hearing thresholds in the left ear.
2 kHz is lateral difference in susceptibility to noise damage.
limited frequency considered
Nageris et al. 2007 [103] Case series 4277 army personnel files age 16–55 3–6 kHz (PTA) mild loss = 25–40 dB HL moderate loss = 41–60 dB HL severe loss = 61–90 dB HL asymmetry = different grade 50% symmetrical.
34.2% left asymmetrical NIHL. 16.3% right asymmetrical NIHL
No significant differences in: age, sex, type of noise, protection, length of exposure, handedness, acoustic reflex.
Simpson et al. 1993 [202] Correctional study 1667 audiometric records of 10 industries 1367 males, 300 females mean age 32.7 and 33.5 2, 3,4 kHz (average threshold) Interaural difference = L-R
laterality >5 dB
80% unilateral with left 42% and right 38%.
Baseline hearing asymmetry appears to be a precursor to unilaterality with 63% in the better ear.
no recordof otologic background, no noise exposure history.
Hong et al. 2005 [60] Cohort study 623 operating engineers mean age 42.96 male 92% 0.5,1, 2, 3, 4, 6, 8 kHz (PTA) Asymmetry:
>15 dB at 0.5,1,2 kHz >30 dB at 3,4, 6 kHz
19% of workers had asymmetrical hearing loss. Significant poorer hearing in the left ear, especially at 4 and 6 kHz Use of hearing protection devices resulted in better hearing but in low use
Fernandes et al. 2010 [94] Case series 208 clients with hearing loss for compensation; age 36–73 203 males, 5 females 0.25–6 kHz (hearing threshold) Asymmetry:
>10 dB for 2 frequencies >15 dB for one frequency
22.6% of clients had asymmetrical hearing loss. Left side had greater loss in 60% of cases. MRI showed no central pathology
Chung et al. 1983 [95] J Occu Med Cohort study 244 shingle sawyers all males age 20–59 0.5,1, 2, 3, 4, 6, 8 kHz (average single frequency threshold) not defined Asymmetry of hearing loss is significant but small compared to general industrial population especially at low frequencies. 101/244 had history of shooting. Hearing protection not well-defined. Small difference of 2.8 dB to left side.
Alberti et al. 1979 [1] Case series 1873 patients with hearing loss for WCB 0.5,1, 2, 4 kHz (PTA) asymmetry >15 dB 15% had asymmetrical hearing loss 5.2% attributed to noise exposure no treatable disorder found after extensive investigations.
Robinson et al. 1985 [111] Case–control series 63 subjects with noise exposure (94 dB) of lOrs 97 normal control subjects 0.5–6 kHz (hearing threshol) Interaural difference = L -R asymmetry >15 dB 10% left-right difference at 4 kHz. small sample variable audiogram shapes
Berg et al. 2014 [92] Cohort study 355 young workers age 29–33 68.5% men follow-up <16 years 0.5,1, 2, 3, 4, 6, 8 kHz (hearing threshold) not defined Asymmetry at >2 kHz in men
Increased asymmetry with increased levels of hearing loss Asymmetry larger in men
Asymmetry varies with shooting exposure No head shadow effect on asymmetry
Dobie et al. 2014 [91] Case–control series 1381 men with noise 80–102 dB
663 men with noise <80 dB
occupational noise exposure
0.5,1, 2, 3 kHz (PTA) 3,4, and 6 kHz (PTA) not defined no significant asymmetry attributable
to current occupational noise exposure
Left ears were 1–2 dB worse than right ears for both groups
 
Dufresne et al. 1988 [96] Case series 602 WCB claims 0.25–8 kHz (hearing threshold) not defined more hearing loss in left ear compared to right ear (5–30 dB) in truck drivers, but not significant for others small sample of truck drivers (n = 10)
Segal et aI. 2007 [99] Cohort study 429 workers
241 (56.2%) with noise exposure (hearing threshold)
188 patients (43.8%) without
79.3% men with SNHL (>29 dB)
0.25–8 kHz (hearing threshold) not defined in noise exposed group, left ear has higher threshold in men. no significant difference left-right in group wihout noise exposure.  
Zapala et al. 2012 [203] Case series Case series n = 5661 benign assymmetry n = 85 vestibular schannoma 0.25–8 kHz
(PTA)
asymmetry < 20 dB Greater asymmetry in self-reported noise exposure history. Largest asymmetry at frequencies >1 kHz Asymmetry increased with age Small differences in asymmetry:
Males (5.14 dB) at 3 and 4 kHz
Females (5.8 dB) at 4 kHz
Royster et al. 1980 [90] Cohort study industrial noise exposure 14186 (75.9% male) 0.5–6 kHz (hearing threshold) not defined right ears are significantly lower threshold Asymmetry is largest for frequecies >2 kHz Mean differences in asymmetry re small (l–5 dB).
Kannan et al. 1974 [100] Review n = 172 50% male l–8 kHz (mean threshold) difference L-R >0 dB Right ear significantly better hearing than left in males only No data about the extend of noise exposure
  1. Abbreviations: HFA high frequency average, HTL hearing threshold level, kHz kilohertz, NIHL noise induced hearing loss, PTA pure tone average, SNHL Sensorineural hearing loss, STS standard threshold shift, TTS temporary threshold shift, WCB workers’ compensation board, dB decibel, L left, R right