The primary mission of the DCCT/EDIC study is to determine the effects of glycemic control and of non- hyperglycemic risk factors on the complications of type 1 diabetes. Persons with type 1 diabetes may have a greater prevalence of hearing loss than comparable non-diabetic individuals. Whether hearing loss is altered by the degree of present or past glucose control or the presence of other diabetes complications is unknown. The DCCT/EDIC cohort provides an excellent opportunity to characterize hearing impairment in type 1 diabetes owing to its long term follow-up of the cohort (30 years). We propose to utilize both a hearing questionnaire and pure tone audiometry testing to define the auditory capability of the entire DCCT/EDIC cohort, to be compared with the results of like assessments in a comparable group of approximately 260 individuals without diabetes, We anticipate that at least 1,100 of the 1,350 surviving EDIC volunteers will volunteer. A hearing questionnaire will be administered by each clinic. Standardized pure tone audiometry testing will be done by each clinic. The primary outcome is the prevalence of hearing impairment based on a mean of the pure tone average of thresholds at 500, 1000, 2000, and 4000 Hz. Hearing impairment will be defined as a pure tone average greater than 25 dB.
The Specific Aims of this proposal are: 1) To determine whether hearing impairment, based on both self-administered questionnaire and measurement of air conduction pure tone thresholds at various frequencies, is more prevalent in the DCCT/EDIC cohort than in a control group without diabetes;2) To assess the association of hyperglycemia, as measured by the mean A1C over ~30 years of the DCCT/EDIC study, with the prevalence and extent of hearing impairment;3) To determine whether the prevalence and extent of hearing impairment differs between the prior DCCT intensive treatment group versus the conventional treatment groups;and 4) To evaluate whether other determinants (e.g., demographic, clinical status, biochemical parameters, behavioral characteristics, and environmental) are related to the prevalence and extent of hearing impairment in the DCCT/EDIC cohort. The above protocol will have greater than 90% power to detect a two-fold difference in the odds of having a hearing loss between the controls and the DCCT/EDIC volunteers. The results will establish the hearing capabilities of individuals with type 1 diabetes compared to non diabetic controls, the impact of glycemic control, the presence of other diabetic complications on hearing, and the identification of hearing impairment risk factors (demographic, clinical, biochemical, behavioral, and environmental). We anticipate that these data will lead to audiological screening and testing recommendations that will have a major quality of life health benefit for all individuals with type 1 diabetes.
The proposed study will identify the causes of hearing loss in people with type 1 diabetes. It will determine if glucose control is important and if it is, to wha degree it contributes to impaired hearing. From this information, national recommendations and guidelines can be published to prevent and/or treat this complication of diabetes.