The Distribution Of NIHL Among Noise Exposed Workers And The Genomic Association Of MiR-96 In Susceptibility To Hearing Loss

Noise is the most frequent occupational hazard and Millions of workers are exposed to harmful noise.Long-term exposure to loud noise or excessively loud impulse noise>85(A)(5-8 hours daily),particularly over a long period of time,can damage hair cells of Corti in the inner ear,and lead to a progressive noise-induced hearing loss(NIHL).Despite the continuous research and public health intervention program,there is high prevalence of noise-induced hearing loss among noise-exposed people,especially in developing countries due to the high rate of industrialization.This study aimed at analyzing the prevalence of noise-induced hearing loss,identifying risk factors in NIHL,in Nanjing Jiangsu province,China,and identifying vulnerable subgroups via genomic analysis by determining the association of expression of miR-96 and susceptibility to noise-induced hearing loss via matched case-control study.1.The distribution characteristics of noise induced high-frequency hearing lossMethods:10,922 noise-exposed workers were selected,among different workers from different industries.A questionnaire was used to collect personal information from the study population.A occupational physical examination was performed in medical center for occupational health examination.Pure tone audiometry was evaluated for all participants by an audiologist in the sound attenuating chamber with a background noise<5dB(A).Audiometry was done for the two ears of each subject at low(LFA of 250Hz to 2kHz)and high(HFA of 4kHz-8kHz)frequency audiometry,Hearing was considered normal when pure-tune audiometry(PTA)was<25dB,moderate when PTA is 26-39,PTA>40 was considered severe.A Univariate logistic regression analysis was used to assess the association between hearing loss and risk factors variables while multivariate logistic regression with backward elimination method was performed to determine the most important risk factors for hearing loss,while controlling for confounding factors.Results:The result from our study showed that 67.34%of people had a normal hearing threshold and the prevalence of high-frequency noise-induced hearing loss was 32.66%,with 21.24%and 11.42%having moderate,severe hearing loss respectively.The prevalence rate of hearing loss was significantly higher in the right ear than left ear((x2)p<0.001).Univariate logistic regression showed that there was an association between hearing loss and age,gender,work duration,exposure duration,Systolic and diastolic blood pressure.Multiple logistic regression models to evaluate the strength of association between hearing loss reveals that on a multivariate analysis,a trend of positive significant association was observed,gender(OR 2.26 CI=1.71-2.97),age(OR 1.24 CI=1.195-1.286)exposure duration(OR 1.038 CI=1.031-1.045)and DBP(OR 1.013 CI=1.007-1.019)A greater percentage of hearing loss is in the male population.The percentage of hearing loss in male and female is 34.45%and 22.02%respectively.The prevalence and severity of hearing impairment increased significantly with age and duration of exposure.Also,there was 34.36%prevalence of hypertension among those with hearing loss.Conclusion:From our study,the result showed that the prevalence noise-induced hearing loss among occupational noise exposed workers in Nanjing was 32.66%.It suggested that there is urgent need for effective noise control or hearing loss prevention program in workplace should be immediately assessed and implemented.2.Genomic association of miR-96 to susceptibility to hearing loss:a case and control studyMethods:150 subjects were requited for a case-control study.The Case(n=75)comprised of the subject exposed to noise of about ? 80dB(A)diagnosed with NIHL.The control group(n=75)comprised of the subject without Hearing loss but also exposed to noise of about ?80dB(A).RNA was extracted from WBC in venous Blood.Trizol reagent was used in extracting the RNA and RT-PCR was done to analyze the expression of miR-96,by strictly following the manufacturer's protocol.Results:The result indicated that the expression of miR-96 gene was lower in subjects with NIHL compared to people with no hearing loss(control).The expression of miR-96 was 0.72 fold lower in cases with hearing loss relative to controls with no-hearing loss.Wilcoxon sign rank test showed no significant difference in the expression of miR-96 between case and control groups(p=0.121)Conclusion:Micro RNA have been known to play important role in gene regulation,Results from this study can be candidate microRNA for susceptibility screening in the population and therapeutic basis for treatment of noise induced-hearing loss in dealing with problem associated with hearing-loss,however further research are need to know the multiple role,target genes of miR-96,and effects on regulation of genes associated with other systems such as the cardiovascular system,and the central nervous system and the mechanism of how mir96 influence the susceptibility of hearing loss caused by noise.General SummaryHearing loss is regarded as the third most common occupational disease,hence it is a major public health concern since millions of people are exposed to noise and risks developing noise-induced hearing loss and other related complications.Despite the increased number of studies toward understanding their etiologies and the rapid advances in therapeutic options,there is still much to learn and as yet,little can be done to prevent their disabling and devastating effects,this study aimed at analyzing the distribution of noise-induced hearing loss and association of miR-96 in genomic susceptibility to noise-induced hearing loss.The result from a descriptive observation study showed that the prevalence of high-frequency noise-induced hearing loss was 32.66%.The prevalence is associated with increasing age and exposure duration.And finally,a case control study showed a difference in the fold expression of miR-96.Results from this study suggest that there is high prevalence of hearing-loss and more public health interventions are needed,also,the difference in expression of miR-96 might be a therapeutic basis in treatment and prevention of hearing loss,however further research are required.