Incidence of Noise induced Hearing Loss among Metropolitan City Traffic Police Personnel

INTRODUCTION: The term noise induced hearing loss is related to reduction in auditory acuity associated with noise exposure. This situation may be temporary and is described as temporary threshold shifts (TTS). The hearing loss may be from hours to days and recovered within 16 hours to 48 hours. The hearing loss may be permanent and described as permanent threshold shift (PTS). PTS may occur following single episode of noise exposure. PTS shifts divided into Acoustic trauma and Noise included hearing loss. Acoustic trauma results from single exposure to an intense sound and leads to an immediate hearing loss. NIHL results from prolonged noise exposure that is more than 85dB of sound level. It depends on the intensity, frequency and duration of the noise exposure. The pure tone audiometry shows characteristic notch with maximum reduction in sensitivity to stimulation in the range from 3 to 6 kHz and recovery at 8 kHz. NIHL results from loss of structural hair cell function. NIHL associated with other causes of hearing loss may not be present with the characteristic 4kHz notch. Absence of the notch does not excluded noise induced hearing loss. Pure tone audiometry is the corner stone of investigation to find out the noise induced hearing loss. And to find out the earlier pathology of hair cell dysfunction before the NIHL present clinically, Otoacoustic emission is the best investigation. AIMS OF THE STUDY: 1. To evaluate the incidence of noise induced hearing loss among Metropolitan city traffic police personnel. 2. To evaluate the degree of hearing loss with respect to the amount of noise exposure. 3. To evaluate the duration of noise exposure with respect to the development of hearing loss. MATERIALS AND METHODS: AIMS AND OBJECTIVE: To find out the incidence of noise induced hearing loss among metropolitan city traffic police personnel. Study Place: Government General Hospital, Chennai 600003. Collaborating department: Upgraded Institute of Otorhinolaryngology, Department of Neurotology, Department of Audiology. Study Design: Prospective. Study Period: February 2010 TO April 2010. Inclusion Criteria: Police personnel working in Chennai city as traffic Regulators. Exclusion Criteria: People with previous ear disease like CSOM, congenital malformations, People with previous ear surgeries, People on ototoxic drugs, head injury, any other major exanthematous illness, People with positive family history of HOH. INVESTIGATION: Pure Tone Audiometry [PTA]. CONCLUSION: All the patients were underwent Pure Tone Audiogram. The following observations were made. 1. The incidence of Noise Induced Hearing Loss was 55.2%. 2. The most common age group affected was more than 40 years, mean age group was 44.55 years. 3. The most of the NIHL cases were mild type - 46.7%, moderate-7% & severe - 1.5%. 4. Bilateral NIHL was common when compared to the unilateral hearing loss. Bilateral-42.1% and unilateral-13.1%. 5. There was considerable relationship between the duration of noise exposure and hearing loss, more than 5 years of work cause significant hearing loss- 54.7%. 6. When intensity of noise exposure was high, the hearing loss is early and more. Mean level of noise exposure was 95.02dB.