- Published on 17 November 2014
Researchers in Norway have found slightly higher hearing loss in older railway workers compared with reference groups not exposed to noise. Noise-induced hearing loss (NIHL) accounts for more than 60% of occupational disorders reported to the Norwegian Labor Inspection Authority, according to the publication. Railway workers performing maintenance on trains and tracks are thought to be at risk of developing work-related NIHL since they are exposed to noise levels of 75-90 dB(A), with peak exposures of 130-140 dB(C).
The study, carried out by researchers at the Department of Occupational Medicine and Epidemiology at the National Institute of Occupational Health, Oslo, Norway, followed a cross-sectional design and investigated hearing thresholds and the prevalence of audiometric notches. It included 1897 train maintenance workers and 2730 track maintenance workers all exposed to noise, as well as 2872 railway traffic controllers and office workers who were not exposed to noise, as a control group. All participants were male.
The study found that workers aged 45 years or older had a minor mean hearing loss in the 3-6 kHz range of 3-5 dB. Hearing loss was lower in workers below this age. Audiometric notches were slightly more prevalent in the noise-exposed group, at 59-64%, compared with the control group at 49%, for all ages.
The authors conclude that the lower levels of hearing loss in younger workers may be related to a shorter period of exposure, preventive measures, or hearing protection that has become more commonly available in recent years. They highlight the difficulty in distinguishing between NIHL and age-related hearing loss based solely on audiograms.
Source: Lie A, et al. A cross-sectional study of hearing thresholds among 4627 Norwegian train and track maintenance workers. BMJ Open. 2014 Oct 16;4(10):e005529.