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Background and Objective: Aircraft as a safe means of transportation may cause occupational diseases and hearing loss. Prevention should be implemented for airport employee. This study was done to detemine the scale of hearing loss among Isfahan airport employees in 2005. Materials and Methods: This historical cohort study was conducted among Isfahan International airport employees. 80 employees were selected in four different case groups, the control group consist of two sub-gourps. The sub-group I (18 subjects) including the adminstrative airport employees (low noise exposed) and the sub-group II (32 subjects) including non-airport employees (non-noise exposed). The sound pressure level was measured and equivalent level (Leq) was calculated for all groups. Also the history of participants about past noise exposure and other confounding variables was detrmined by a questionnaire. Pure tone audiometry was carried out on conventional frequencies (0.5-8 KHz). Results: The mean age of subjects was 40.03±9.75 and 37.85±8.15 for exposed and non-exposed groups respectively. Leq (noise equivalent level) for Ramp and traffic workers was estimated more than 95 dBA. 35.7% (n=10) of Ramp workers were suffering in their right ear from noise induced hearing loss (26-40dB) and 32.1% (n=9) of them in their left ear. Relative risks of noise induced hearing loss in Ramp workers in comparison with control group were 9.4 and 7.5 for right and left ears. A siginificant difference was found between the hearing thresholds of exposed and non-exposed groups (P<0.05). Conclusion: This study showed that occupational exposure to noise cause hearing loss among airport employee. It is suggested strategies of noise assessment and prevention should be implemented for airport employees.

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Background and Objective: Multiple sclerosis is one of demyelinating disorder of CNS that is an uncommon cause of the sensorineural hearing loss. This study was done to determine the hearing loss in multiple sclerosis patients.

Materials and Methods: This case-control study was performed on 60 (44 women, 16 men) multiple sclerosis patients and 38 (27 women, 11 men) normal subjects by pure tone audiometery, otoacustic emissions and auditory brainstem responses in Gilan provine, Iran during 2010-11. Data was analyzed by using SPSS-17, Chi-Square and Fischer tests.

Results: 12.5% of case and 3.9% of the control ears had abnormal pure tone audiometery (P<0.05). The frequencies of abnormal HF-pure tone audiometery and two modalities of otoacustic emission did not show any significant differences in two groups. Abnormal autidory brainstem response of ears were observed in 20% and 9.2% of cases and controls, respectively (P<0.05). 20% of case and 9.2% of the control ears had abnormal auditory brainstem response (P<0.05). The absolute latencies of waves I, II and V had not significant differences between two groups. Inter peak latencies of I-III and III-V waves were observed in 10% and 11.7% in cases ears and 1.3% and zero percent in controls, respecticely. 6.7% of cases and 2.6% of control ears had retrocochlear abnormality.

Conclusion: Hearing loss detected by pure tone audiometery and auditory brainstem response is more common in multiple sclerosis compared to normal population.