Asymmetry in noise-induced hearing loss: Relevance of acoustic reflex and left or right handedness

OBJECTIVE: Noise-induced hearing loss (NIHL) is more severe in the left ear than the right ear. The aim of this study was to examine the possible association of handedness and acoustic reflex parameters on right or left NIHL predominance. STUDY DESIGN: Retrospective case review and prospective series. SETTING: Tertiary center. PATIENTS: Three samples were studied: 1) the files of 4,277 army personnel with NIHL were reviewed to analyze the relation between the side affected and age, sex, duration of noise exposure, and acoustic damage; 2) an additional 119 army personnel with NIHL were evaluated for the possible association of handedness and NIHL asymmetry; and 3) fifty-one normal-hearing subjects were tested for threshold and latency of acoustic reflex by handedness. INTERVENTION: None. MAIN OUTCOME MEASURE: Differences in NIHL asymmetry by background and noise-related variables and handedness. RESULTS: NIHL was more pronounced in the left ear, regardless of demographic characteristics, noise exposure parameters, acoustic reflex measures, or handedness. CONCLUSION: The asymmetry in hearing loss severity may be attributed to the cortical pathways, specifically to the more pronounced efferent auditory system on the right side, which reduces the susceptibility of the right ear to cochlear insult.