Characteristics of Tinnitus in Individuals with Noise Induced Hearing Loss (NIHL): A Systematic Review

Abstract

Background: Exposure to noise at the workplace, as well as personal listening devices, is a significant risk factor for hearing loss or tinnitus in young adults and adolescents. Noise exposure causes not just hearing loss but also tinnitus and its associated co-morbidities which is permanent, causing damage to hearing cells within the inner ear resulting in decreased quality of life. Tinnitus is much more common (24%) among noise-exposed workers than in the general population (14%). Recent studies have reported more severe hearing loss and severe subjective tinnitus in individuals with noise induced hearing loss (NIHL) (Kang et al., 2021). There is a need for a systematic study on this subject because there hasn't been a current update on all of the major and minor tinnitus features in cases with NIHL. Objective: The present study aims to review the significant studies conducted in the past ten years (2010-2020) reporting the characteristics of tinnitus in individuals with noise induced hearing loss (NIHL). Method: A systematic search in the electronic databases like Google Scholar, PubMed, JSTOR, AJOL, COCHRANE & Science direct was carried out using the appropriate key Words. Following the PRISMA guidelines and based on inclusion and exclusion criteria 12 research articles were finalized and reviewed which included data collected on subjective tinnitus in individuals with noise induced hearing loss (NIHL). Only research articles containing studies on adult subjects were included in the review. Results: This systematic review throw light on the 10 different tinnitus characteristics in individuals with noise induced hearing loss (NIHL). Based on that the major characteristics were tinnitus loudness and pitch, laterality, severity and discomfort, duration, type and sex differences which was report by most of the articles whereas minor characteristics include frequency of occurrence of tinnitus, tinnitus onset, tinnitus subjective quality and loudness grading which was reported in very few publications. Finding suggested that tinnitus was mostly bilateral, followed by left-sided, and described as buzzing or high-pitched in individuals who had NIHL. There was a correlation between age, length of tinnitus, and hearing loss. Tinnitus onsets ranges from acute (within one month) to more than a year. The severity of tinnitus reflects the level of hearing loss. The intensity of tinnitus is affected by the degree of NIHL. No significant ear and gender difference was noticed. Tinnitus or hearing loss affects about one-fifth of young adults (<40 years old), indicating that future hearing difficulties are on the rise. Conclusion: Exposure to noise in the workplace, as well as personal listening devices, is a significant risk factor for hearing loss or tinnitus in young adults and adolescents. Rock musicians are at an increased risk of developing chronic tinnitus. Overexposure to noise causes not just hearing loss but also tinnitus and its associated co-morbidities, which results in deterioration of quality of life. Noise induced tinnitus affects a substantial proportion of young adults, yet they do not use hearing protection as a result, probably due to a lack of information about the consequences of loud music. Young adults should see tinnitus as a warning sign rather than a natural result of listening to loud music. This basic research gives us the better understanding of various characteristics of tinnitus encountered in people with NIHL.