Ann-Christin Johnson1, Renata Bogo1,2, Ahmed Farah3, Kjell K Karlsson2, Per Muhr1, Mattias Sjöström4, Eva B Svensson1, Åsa Skjönsberg1,2, Magnus Svartengren5. 1. a Department of Clinical Science, Intervention and Technology, Unit of Audiology , Karolinska Institutet , Stockholm , Sweden. 2. b Department of Audiology and Neurotology , Karolinska University Hospital , Huddinge , Sweden. 3. c Department of Monitoring and Evaluation, Public Health Agency of Sweden , Stockholm , Sweden. 4. d Department of Occupational Medicine , Karolinska Institutet , Stockholm , Sweden , and. 5. e Department of Medical Sciences , Uppsala University , Uppsala , Sweden.
Abstract
OBJECTIVE: The aim was to investigate the influence of environmental exposures on hearing loss in a twin cohort. STUDY SAMPLE: Male twins born 1914-1958, representing an unscreened population, were tested for hearing loss at two occasions, 18 years apart. DESIGN: Clinical audiometry and a questionnaire were performed at both time points in this longitudinal study. Noise and solvent exposure were assessed using occupational work codes and a job exposure matrix. Hearing impairment was investigated using two different pure tone averages: PTA4 (0.5, 1, 2, and 4 kHz) and HPTA4 (3, 4, 6, and 8 kHz). RESULTS: Age affected all outcome measures. Noise exposure between time point one and two affected the threshold shifts of PTA4 and HPTA4 more in participants with a pre-existing hearing loss at time point one. Lifetime occupational noise exposure was a risk factor especially for the low-frequency hearing threshold PTA4. Firearm use was a statistically significant risk factor for all outcome measures. CONCLUSIONS: Pre-existing hearing loss can increase the risk of hearing impairment due to occupational noise exposure. An increased risk for NIHL was also seen in the group with exposures below 85 dB(A), a result that indicates awareness of NIHL should be raised even for those working in environments where sound levels are below 85 dB(A).
OBJECTIVE: The aim was to investigate the influence of environmental exposures on hearing loss in a twin cohort. STUDY SAMPLE: Male twins born 1914-1958, representing an unscreened population, were tested for hearing loss at two occasions, 18 years apart. DESIGN: Clinical audiometry and a questionnaire were performed at both time points in this longitudinal study. Noise and solvent exposure were assessed using occupational work codes and a job exposure matrix. Hearing impairment was investigated using two different pure tone averages: PTA4 (0.5, 1, 2, and 4 kHz) and HPTA4 (3, 4, 6, and 8 kHz). RESULTS: Age affected all outcome measures. Noise exposure between time point one and two affected the threshold shifts of PTA4 and HPTA4 more in participants with a pre-existing hearing loss at time point one. Lifetime occupational noise exposure was a risk factor especially for the low-frequency hearing threshold PTA4. Firearm use was a statistically significant risk factor for all outcome measures. CONCLUSIONS: Pre-existing hearing loss can increase the risk of hearing impairment due to occupational noise exposure. An increased risk for NIHL was also seen in the group with exposures below 85 dB(A), a result that indicates awareness of NIHL should be raised even for those working in environments where sound levels are below 85 dB(A).