[Ultrahigh-frequency hearing thresholds in middleaged and elderly healthy adults]

Objective:To investigate the ultrahigh-frequency(UHF) hearing thresholds in middle-aged and elderly healthy subjects .Method: Healthy subjects(age range: 50-69 ) were divided into two groups,i.e.50-59 year-old group and >59-69 year-old group.Each subject was tested with both conventional-frequency(0.25,0.50,1.00,2.00,4.00,6.00 and 8.00 kHz) and ultrahigh-frequency(9.0,10.0,11.5,12.5,14.0,16.0,18.0,and 20.0 kHz) audiometry.UHF was performed twice to evaluate the reliability.The best hearings among 20-29 aged healthy adults were considered as normal controls.Results:Seventy five middle-aged and elderly subjects were included,with 39 subjects(78 ears) being 50-59 years old and 36(72 ears) being >59-69 year-old.Eighteen subjects(36 ears) aging from 20 to 29 were considers as controls.For the conventional-frequency,the hearing thresholds in middle-aged and elderly people were significantly higher than those in young people(all P<0.05),especially at ≥4 kHz.Although the conventional-frequency thresholds in >59-69 year-old group were higher than those in 50-59 year-old,the difference was significant just at 4 kHz(P<0.05).The UHF thresholds in middle-aged and elderly people were significantly higher than those in young people(all P<0.05).The thresholds at 9,10,11.5 and 12.5 kHz in >59-69 year-old people were significantly increased than those in 50-59 year-old counterparts(all P<0.05).Hearing threshold at ≥12.5 kHz couldn't be detected in some subjects in middle-aged and elderly group.The response rate at UHF in >59-69 year-old people were just higher than that in 50-59 year-old counterparts (P>0.05),and none responded at 18 and 20 kHz.The standard deviations(SDs) for <14 kHz in 50-59 year-old and for <11.5 kHz in >59-69 year-old subjects,were both higher than that in 20-29 year old counterparts.Above 6 kHz,the SDs in 50-59 year-old subjects were significantly higher than those in >59-69 year-old subjects(all P<0.05).Conclusion:For middle-aged and elderly people,the hearing loss may occur from 4 kHz.Hearing thresholds at UHF were increased with age,and it might be used as an early indicator for age-induced hearing loss.However,the UHF sensitivity decreased as the frequency increased beyond 14 kHz.