Diabetes and risk of hearing impairment in adults: a meta-analysis.

CONTEXT Recently, several studies have investigated the relationship between diabetes and hearing impairment, but results were inconsistent. OBJECTIVE Our objective was to compare the prevalence of hearing impairment between diabetic and nondiabetic adults. DATA SOURCES We performed a systematic literature search using MEDLINE (1950 to May 30, 2011) and EMBASE (1974 to May 30, 2011). STUDY SELECTION Cross-sectional studies were included if data on numbers of hearing-impaired and non-hearing-impaired cases with diabetes were presented. Hearing impairment was limited to that assessed by pure-tone audiometry that included at least 2 kHz of frequency range and was defined as progressive, chronic, sensorineural, or without specified cause. DATA EXTRACTION Two authors independently extracted relevant data. Odd ratios (ORs) of hearing impairment related to diabetes calculated in each study were pooled with the random-effects model. DATA SYNTHESIS Data were obtained from 13 eligible studies (20,194 participants and 7,377 cases). Overall pooled OR (95% confidence interval) of hearing impairment for diabetic participants compared with nondiabetic participants was 2.15 (1.72-2.68). OR was higher in younger participants (mean age, ≤60 yr) than in those over 60 yr among which the OR remained significant (2.61 and 1.58, P = 0.008). The strength of the association between diabetes and prevalence of hearing impairment was not significantly influenced by whether participants were matched for age and gender (P = 0.68) or whether participants chronically exposed to noisy environments were excluded (P = 0.19). CONCLUSIONS Current meta-analysis suggests that the higher prevalence of hearing impairment in diabetic patients compared with nondiabetic patients was consistent regardless of age.