Hearing loss (HL) and vestibular dysfunction (VeD) are common conditions resulting from inner ear dysfunction that often go undetected until the deficit is pronounced. Further, HL related to diabetes initially leads to high frequency HL, a communication deficit may lead to isolation, depression and low quality of life. Longer and more severe hyperglycemia may affect low/mid frequency HL, but the association is currently unclear. Physiologic damage is of the permanent, sensorineural type and therefore, prevention is accomplished by early detection and intervention. Vestibular dysfunction occurs through the same mechanisms as HL, and may lead to imbalance and dizziness, which are associated with falls and loss of independence. While the association between type 2 diabetes (T2D) and HL is well established, less is known about T2D and vestibular dysfunction. Data on prediabetes (preD) and inner ear dysfunction are also limited. The Year 35 Coronary Artery Risk Development in Young Adults (CARDIA) study clinic visit (2020- 2021) will be used to recruit participants for an ancillary study to examine the roles that cross-sectional and longitudinal measures of preD and T2D collected over 35 years from young adulthood play in HL and VeD in middle age among a well-characterized cohort of black and white men and women. HL will be measured using an automated audiometry protocol that is suitable for population-based hearing assessment in large samples without the requirement of specialized audiologists. VeD will be assessed with novel video head impulse testing to capture ear-level vestibular system integrity. PreD and T2D will be determined based on fasting glucose at Year 35, and historically via fasting glucose, oral glucose tolerance testing, medication use and/or hemoglobin A1c, and will capture both degree and duration of hyperglycemia. The CARDIA cohort will be ages 53-65 years at the Year 35 clinic visit; because hearing sensitivity decreases by approximately 10 dB per decade starting around the age of 60 years, CARDIA is now at the ideal age to capture HL prior to age-related declines while having sufficient prevalence and incidence of both preD and T2D; while VeD is not a clinical condition per se, this research will provide normative data for a population- based study. Therefore, this ancillary study proposes to examine the following aims: 1) to assess the association between both T2D and preD and vestibular dysfunction; and 2) to characterize the associations of preD and T2D with overall, low/mid, and high frequency HL cross-sectionally and using trajectory analysis for longitudinal glycemia trends. CARDIA provides a unique opportunity to connect preD and T2D developing from young adulthood with HL and VeD in middle age. Integration of this research into the existing CARDIA clinic visit is an efficient and cost-effective way to maximize recruitment in a cohort that has had stable retention.
While hearing loss (HL) can be related to age (presbycusis), disease, heredity, and chronic noise exposure, hyperglycemia irreversibly affects the vasculature and neural system of the inner ear, damaging both the auditory nerve and the vestibular system, which in turn may contribute to HL and vestibular dysfunction (VeD). VeD typically manifests as vertigo, dizziness, and imbalance, and is a strong predictor of future falls and fracture in the elderly. The proposed research will examine the associations of diabetes and prediabetes over 35 years of follow up with HL and VeD in a population-based cohort of middle-aged black and white men and women to better understand risk factors and prevention.
