Background: Diabetes mellitus (DM) and hearing impairment are both highly prevalent in older adult populations, but how the impact of diabetes on hearing varies by age is not well-studied.
Material/Methods: The subjects were 2306 adults aged 40 to 86 years who participated in a population-based study of aging, and were divided into 2 age groups, 40–64 years and 65–86 years, for cross-sectional analysis. Air-conduction pure-tone thresholds at octave intervals from 125 to 8000 Hz were obtained. Outcomes were categorized in relation to presence or absence of DM. Hearing levels at 7 frequencies were set in the general linear model as objective variables with adjustment for confounders. Explanatory variables were age (<65 years vs. ≥65 years), DM (absence vs. presence), and interaction between age and DM.
Results: A statistically-significant adverse effect of DM on hearing was observed. This effect varied by age at the higher frequencies. The DM-age interaction was not synergistic at any test frequencies. No significant effects of the DM-age interaction were observed below 4000 Hz. In contrast, significant reciprocal effects of the DM-by-age interaction were found at 4000 Hz and 8000 Hz. Diabetes may accordingly affect higher-frequency hearing more strongly in the younger age-bracket.
Conclusions: This study demonstrated that diabetes detrimentally affected hearing in community-dwelling middle-aged and elderly people, and that the effect of diabetes on higher-frequency hearing might be stronger in middle age. Screening for hearing impairment in diabetic patients may provide benefits for intervention or prevention of early presbycusis, particularly in this age group.

Keywords: Linear Models, Japan - epidemiology, Diabetes Complications - complications, Demography, Auditory Perception, Aging - pathology, Aged, 80 and over, Age Distribution, Presbycusis - epidemiology, Prevalence