title: Cochlear dysfunction in type 2 diabetes: a complication independent of neuropathy and acute hyperglycemia.
abstract: The effects of type 2 diabetes on evoked otoacoustic emissions (e-OAEs) elicited by clicks in subjects with normal hearing and the involvement of the central (CNS) and peripheral nervous system and acute hyperglycemia were investigated. In study 1, 110 type 2 diabetic patients and 106 control subjects matched for age and gender were investigated by e-OAEs. Central and peripheral neuropathy were evaluated respectively by auditory brainstem responses (ABRs) and according to San Antonio Consensus Conference criteria. In study 2, 10 healthy and 10 type 2 diabetic men matched for age, all with normal e-OAEs, underwent a 5-hour hyperglycemic clamp study. e-OAE tests were performed before and during the hyperglycemic clamp. In study 1, e-OAEs were impaired in 51.8% (57 of 110) of the diabetic subjects, in comparison to 4.7% (five of 106) of the control group (P < .0001). Diabetics with impaired e-OAEs (e-OAEs-), in comparison to those with normal e-OAEs (e-OAEs+), were older (51.0+/-5.8 v 45.1+/-6.0 years, P < .001), had diabetes longer (11.5+/-4.4 v 7.0+/-3.9 years, P < .001), achieved poorer metabolic control as judged by hemoglobin A1c ([HbA1c] 6.9%+/-0.4% v 6.5%+/-0.3%, P < .001), and had more peripheral neuropathy (46% v 23%, P < .02). No difference was observed between e-OAEs- and e-OAEs+ subjects for retinopathy or nephropathy. Nevertheless, when the duration of diabetes was corrected by multiple regression analysis, the correlation between sensorineural damage and peripheral neuropathy lost significance (P = .12). Diabetic groups (e-OAEs+ and e-OAEs-) showed greater latency in waves I, III, and V and greater interwave latency for waves I to V than the control group, but there was no significant difference in ABRs between e-OAEs+ and e-OAEs- subjects. In study 2, there were no significant changes in e-OAE intensities compared with basal values during the entire hyperglycemic clamp in either type 2 diabetic or control subjects. No difference was observed between the two groups at each time of the clamp. Thus, type 2 diabetic subjects show a higher rate of compromised e-OAEs than healthy individuals. The e-OAE dysfunction does not associate with either an injury to the auditory nervous pathway or diabetic microvasculopathy. The apparent interference of peripheral neuropathy in e-OAEs loses significance when corrected for the duration of diabetes.
authors.affiliation: Department of Gerontology and Metabolic Diseases, Second University of Naples, Italy.
authors.forename: F C
authors.initials: FC
authors.lastname: Sasso
authors.forename: T
authors.initials: T
authors.lastname: Salvatore
authors.forename: G
authors.initials: G
authors.lastname: Tranchino
authors.forename: D
authors.initials: D
authors.lastname: Cozzolino
authors.forename: A A
authors.initials: AA
authors.lastname: Caruso
authors.forename: M
authors.initials: M
authors.lastname: Persico
authors.forename: S
authors.initials: S
authors.lastname: Gentile
authors.forename: D
authors.initials: D
authors.lastname: Torella
authors.forename: R
authors.initials: R
authors.lastname: Torella
mesh_terms: D000208:Acute Disease; D000328:Adult; D016022:Case-Control Studies; D015834:Cochlear Diseases / Q000097:blood / Q000209:etiology* / Q000503:physiopathology*; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000150:complications* / Q000503:physiopathology*; D003929:Diabetic Neuropathies / Q000503:physiopathology; D016057:Evoked Potentials, Auditory, Brain Stem; D005260:Female; D015309:Glucose Clamp Technique; D006442:Glycated Hemoglobin / Q000378:metabolism; D006801:Humans; D006943:Hyperglycemia / Q000209:etiology / Q000503:physiopathology; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D013997:Time Factors
chemical_list: D006442:Glycated Hemoglobin