Characteristics of Hearing Loss in Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis

A systematic review of CINAHL, Cochrane Library, PubMed, and SCOPUS databases was conducted according to PRISMA guidelines to identify studies evaluating T2DM and hearing loss. Primary outcome measures included continuous measures (mean), proportions (%), proportional difference (∆), and relative risks (RR) with 95% confidence intervals (CI).

A total of 39 studies with 88,395 patients with T2DM and 20,337 controls were included. The mean ages of the T2DM and control groups were 50.3 (range: 19-96) and 46.7 (range: 19-76), respectively, with females comprising 63.8% and 64.3% of the groups. The mean duration of diabetes in the T2DM group was 9.1 years (95% CI: 8.1-10.1), and mean HbA1c of 8.4% (95% CI: 8.1-8.6), while the control group had 4.8% (95% CI: 3.9-5.7). Patients with T2DM had significantly higher prevalence and relative risk of clinically significant hearing loss compared to controls (53.0% vs 25.2%; ∆ = 27.7%, p < .0001; RR = 2.3, 95% CI: 1.1-4.8). In T2DM, 5.0% had conductive, 46.2% sensorineural, and 10.4% mixed hearing loss. According to WHO criteria, the T2DM group exhibited 22.1% mild (26-40 dB), 25.5% moderate (41-60 dB), 8.5% severe (61-80 dB), and 1.7% profound (>80 dB) hearing loss all with statistically significant differences compared controls (p ≤ .0001). In the T2DM group, data on laterality showed 15.0% unilateral and 29.6% bilateral hearing loss, both significantly higher than the controls (p = .008, p < .0001).

This meta-analysis provides most updated estimates of the prevalence and relative risk of hearing loss in patients with T2DM, including details on the classification, laterality, and degrees. The significantly increased risk highlights the importance of incorporating hearing assessments and management into routine care for patients with T2DM.