2.1. Study design and study population
A cross-sectional study was conducted on police personnel
(employed by the RBPF) at nonofficer level who were seen for periodic
medical examination at the OHD during the period of January
2012 until December 2012. Each person had to have been in service
for at least 3 years and a maximum of 30 years. Diagnosis of NIHL
was based on (1) history of occupational noise exposure, (2) bilateral
hearing loss, (3) hearing loss of > 25 dBA at 4,000 Hz frequency
in two consecutive audiograms, and (5) no significant medical
history affecting hearing [11]. Other causes of hearing loss needed
to be excluded such as nonoccupational noise exposure, ototoxic
medications, family history of hearing loss, recent or chronic ear
infections, head and neck injury, radiotherapy to the head and neck,
and history of mumps. New police recruits during this period were
also excluded. Of note, part of the selection criteria to join the RBPF
was absence of any hearing impairment. Smoking and alcohol
consumption were included as part of the demographic data. In
cases where NIHL was diagnosed, the individual was referred to the
Ear, Nose, and Throat department at