Neuroprotective factors and incident hearing impairment in the epidemiology of hearing loss study

Objective Hearing impairment (HI) is common in aging adults. Aldosterone, insulin-like growth factor (IGF1), and brain-derived neurotrophic factor (BDNF) have been identified as potentially protective of hearing. The present study aims to investigate these relationships. Methods The Epidemiology of Hearing Loss Study is a longitudinal population-based study of aging in Beaver Dam, Wisconsin, that began in 1993. Baseline for the present investigation is the 1998 to 2000 phase. Follow-up exams occurred approximately every 5 years, with the most recent occurring from 2013 to 2016. Hearing was measured by pure-tone audiometry. HI was defined as a pure tone average (PTA) > 25 decibels hearing level in either ear. Change in PTA was the difference between follow-up examinations and baseline. Baseline serum samples were used to measure biomarkers in 2017. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated to assess the effect of biomarker levels in the lowest quintile (Q1) versus the highest (Q5) on incident HI and PTA change. Results There were 1,088 participants (69.3% women) at risk of HI included in analyses. The mean baseline age was 63.8 years (standard deviation = 7.0). The 16-year incidence of HI was 54.9% and was higher in men (61.1%) than women (52.1%). In age- and sex-adjusted models, aldosterone (HR = 1.06, 95% CI = 0.82-1.37), IGF1 (HR = 0.92, 95% CI = 0.71-1.19), and BDNF (HR = 0.86, 95% CI = 0.66-1.12) levels were not associated with risk of HI. PTA change was similarly not affected by biomarker levels. Conclusion Aldosterone, IGF1, and BDNF were not associated with decreased risk of age-related hearing loss in this study. Level of Evidence 2b Laryngoscope, 129:2178-2183, 2019