Tympanometry in patients with insulin-dependent diabetes mellitus

Tympanograms were studied in 53 patients with insulin-dependent diabetes mellitus (IDDM) and 42 randomly selected non-diabetic control subjects, aged between 20 and 40 years, using the Madsen Model ZO 73 Impedance Bridge. Subjects with abnormal tympanic membrane, conductive hearing loss and known reason for hearing impairment (e.g. noise damage) were excluded from the study. The mean tympanogram amplitudes in diabetic patients were significantly lower in both ears than those of control subjects. The duration of diabetes and microvascular complications (nephropathy and retinopathy) were associated with decreased amplitudes. These findings indicate that decreased tympanogram amplitudes in patients with IDDM are probably caused by diabetes of long duration and the microvascular complications associated with it.