Effect of basic military training on hearing in the Singapore Armed Forces

Introduction: In the military service, hearing is at risk through exposure to impulse noise from firing and detonations. This study aims at looking into the consequences of military training on hearing acuity, as it would be useful to confirm the effectiveness of the hearing conservation programme in the Singapore Armed Forces.
Methods: A self-controlled study of 118 Singapore military conscripts was carried out, using questionnaires administered by trained personnel and pure tone audiometric assessments performed for both ears. The questionnaire and audiometry were done at the start of basic military training (BMT), with follow-up audiometry done at the end of BMT and one year into vocational military training (VT).

Results: 33 military conscripts were excluded subsequently in latter phases of the study. Of the 85 remaining conscripts, 16.5 percent of the study population were found to have abnormal audiograms at the start of BMT. At the end of the BMT phase, the percentage of enlistees with abnormal audiograms was 9.4 percent. By the end of one year of VT, the percentage of enlistees with abnormal audiograms was still 9.4 percent. Analysis of the differences in number of enlistees with hearing loss was done with the McNemar's test, and was found to be statistically insignificant (p-value equals 0.238).

Conclusion: The prevalence of 16.5 percent abnormal audiograms at the pre-BMT stage is probably related to unfamiliarity with the audiogram testing and/or "temporary threshold shift" effect. There was no significant difference in the number of enlistees with hearing loss upon enlistment and after one year of military training in this cohort of soldiers.