A pilot study comparing hearing thresholds of soldiers at induction and after completion of one year in high altitude area.

Background: Despite so much research in high altitude area, our existing knowledge is still lacking on otological effects of long-term stay in high altitude. This pilot study was conducted to compare the hearing thresholds of army soldiers at induction and after completion of one year in high altitude area (HAA).

Methods: Hearing thresholds of 433 soldiers posted in HAA were recorded using pure tone audiometry at the time of induction and second thresholds after one year of stay in high altitude for frequencies of 500Hz, 1KHzs, 2 KHzs and 4 KHzs. The two sets of hearing thresholds for air conduction were compared using paired "t" test for any statistical significance.

Results: The mean Pure Tone Audiometry (PTA) thresholds for 433 left ears worsened from 9.43dB to 9.65dB at 500 HZs ; 14.02dB to 14.32dB at 1 KHZs ; 15.04dB to 16.09dB at 2KHzs and 18.63dB to 22.59dB at 4 KHZs. Similarly for right ear, PTA thresholds worsened from 9.43dB to 9.69dB at 500HZs; 13.95dB to 14.34dB at 1 KHZs; 15.38dB to 17.26dB at 2 KHZs and from 18.59dB to 23.06dB at 4KHZs. These results are found to be statistically significant (p<0.05) for all frequencies.

Conclusion: This pilot study shows deterioration of hearing thresholds in tested frequencies in both ears after a long stay (one year) in high altitude area. We recommend further structured research on otologic effect of long term stay in high altitude.