Association of different severity of diabetic retinopathy and hearing loss in type 2 diabetes mellitus

Purpose: Microvascular involvement in patients with diabetes mellitus is one of the causes of retinopathy, nephropathy, and neuropathy. The same pathologic processes may occur in the inner ear structures. This casecontrol study aimed to evaluate the hearing thresholds in type 2 diabetic patients with different severity of diabetic retinopathy (DR) and to compare these findings with controls.Materials and methods: We evaluated the hearing threshold in four groups of eligible subjects aged 20-70 years. These groups were controls, diabetic patients with no-DR, with mild-moderate non-proliferative DR (NPDR), and with severe NPDR/proliferative DR (PDR). Each group consisted of 105 subjects. Speech-frequency and highfrequency hearing levels (SFHL and HFHL, respectively) were measured and log-transformed. Analysis of covariance was used. The prevalence rate of moderate or more hearing loss in the groups was estimated.Results: In total, 194 men and 226 women participated. The ratio of means of SFHL and HFHL between PDR and controls was 0.18 and 0.20, respectively. Hearing loss was prevalent in severe NPDR/PDR (adjusted prevalence ratio 3.36 for SFHL and 1.51 for HFHL) compared to controls. Also, the prevalence of high-frequency hearing loss was more in mild-moderate NPDR (adjusted prevalence ratio 1.33).Conclusions: The magnitude of the increase in hearing impairment prevalence between the severe NPDR/PDR patients and controls was about 24% for both SFHL and HFHL. We recommend hearing assessment in the screening of the DR patients.