OBJECTIVE: To explore the function of outer hair cells and its influencing factors in the workers of occupational exposure to low frequency electric and magnetic fields. METHOD: 502 high-strength LF EMFs-exposed workers were taken as the study subjects. The field intensity indicator and noise analyzer were employed for the examination of the electromagnetic energy intensity and noise value at the working sites. Self-administered questionnaires were adopted. Universal hearing screening by distortion product otoacoustic emission (DPOAE) and pure tone audiometry (PTA) were done. 100 workers who had abnormal POAE were taken as the observation group and 100 workers who had normal DPOAE were taken as the control group. The workers need be confirmed with ABR testing when the pure tone threshold of two consecutive frequencies were above 20 dB HL or DPOAE detection in any frequency did not pass. Multiple factor analysis with logistic regression was performed for the risk factors. RESULT: The average electric power density in job locations was 21-38 KV/m, which was higher than national standard (< 5 kv/m). Average noise-level in job locations was 52-65 dBHL, which was within the standard (< 85 dB(A). Questionnaire presented that low frequency electric and magnetic fields might increase the incidence of headache, insomnia and tinnitus in the observed group. The incidence of abnormal DPOAE was higher in the subjects of the observed group (P < 0.01). At 676, 933, 3616, 5 130, 7253 Hz, the DPOAE amplitudes of the observed group workers were significantly lower than the control group. Multivariate analysis showed that the risk factors of abnormal DPOAE included exposure of EMF, length of service, daily exposure time, conservatory measures might be protective factors. CONCLUSION The changes of DPOAE indicated that the exposure to low frequency electric and magnetic fields had a subtle, discreet and localized impairing effects on outer hair cells. Exposure of low frequency electric and magnetic fields, length of service, daily exposure time might be risk factors, conservatory measures might be protective factors.
Auditory Threshold ; Case-Control Studies ; Electromagnetic Fields ; adverse effects ; Hair Cells, Vestibular ; pathology ; Humans ; Magnetic Fields ; adverse effects ; Male ; Noise ; adverse effects ; Occupational Exposure ; Surveys and Questionnaires

Objective: Tailor-made notched music was applied to alleviate the symptoms of chronic idiopathic tinnitus and compared its effectiveness with other existing sound treatment of tinnitus. Methods: Subjects (n=43; ears=75 )were recruited during June 2015 to October 2016 from the out-patients of our hospital. These patients had chronic (longer than 6months) and idiopathic tinnitus, with or without significant sensorineural hearing loss. In the prospective design, the patients were randomly divided into group A (treated with tailor-made notched music) and group B (treated with analogous sound masking), and received the treatment for 3 months. The tinnitus scale, tinnitus questionnaire and audiological findings were evaluated before treatment, and at one month and three months after treatment started. Results: After onemonth of treatment, the effective rate between the two groups was 40.9% and 42.9%, there was no significant difference between the two groups (χ²= 0.017, P=0.897). The average VAS for patients in group A showed more decrease in group A than in group B(VAS: 1.8 vs. 0.8, the percentage : 29.5% vs. 13.6%), but there was no significant difference between the two groups (t=-1.450, P=0.155). After 3 months of treatment, the effective rates were 68.2% and 23.8%, respectively. There was significant difference between the two groups (χ²= 8.503, P=0.004). The difference of the VAS scores between the two groups was statistically significant (t=-3.263, P=0.002), and the VAS score of group A was less.After 3 months of treatment, there was significant decreaseinthe average tinnitus loudness for patients in group A(t=5.569, P<0.01), and there was no significant changein group B(t=-0.953, P=0.374). There was also significant decreasein the scores of tinnitus handicap inventory (THI) (F=7.334, P<0.05), loudness visual analog scale (VAS) (F=20.48, P<0.001), and the proportion of patients with moderate to severe tinnitus(χ²=11.289, P<0.05) in the group A, and there was no significant change in group B(F=2.198, F=0.989, χ²=1.651; P=0.120, P=0.378, P=0.438>0.05). Conclusions Our resultssuggest that long-term normalized listening to tailor-made notched music, can significantly reduce the perceived tinnitus loudness in varying degrees and improve the quality of life of patients. The effects and possible mechanism of this method were discussedin this paper.