Diabetes-related changes in hearing.

OBJECTIVES/HYPOTHESIS Determine the effects on hearing of diabetes mellitus (DM) severity. STUDY DESIGN We conducted a cross-sectional study among Veterans to investigate the relationship of diabetes severity and hearing in randomly selected subjects with (165) and without (137) DM and who had no more than a moderate hearing loss. METHODS Subjects were classified by three age tertiles (<50, 50-56, and 57+ years). Diabetes severity was classified as insulin-dependent (IDDM), noninsulin-dependent (NIDDM), or no DM. Other DM measures included concurrent serum glucose, serum HbA(1c), duration of disease, and several measures of DM-related complications. Pure-tone thresholds were measured in both ears of each subject at frequencies from 250 Hz through 14,000 Hz. Outcome measures were adjusted for age and frequency and analyzed for differences between subject groups using analysis of variance. Contrasts of the mean NIDDM and IDDM thresholds at each frequency to the DM group, and controlled for the effects of frequency, age, and interactions were modeled. RESULTS There was greater hearing loss in younger tertile DM subjects compared to those without DM. Significant hearing differences were at all frequencies for NIDDM subjects, but for IDDM subjects, differences were at 1,000 Hz and below, and 10,000 Hz and above. Over age 50 years, there were significant associations between hearing at low frequencies and IDDM only. Self-report of prior noise exposure did not explain observed differences. CONCLUSIONS Diabetes is associated with an increased risk of hearing loss, and this difference is manifest particularly in adults <50 years old.