The risk of sudden sensorineural hearing loss associated with metformin use in patients with diabetes mellitus has not been fully examined.

It is a retrospective matched-cohort study.

We examined the medical records of patients with diabetes mellitus over 18 years old in Taiwan’s National Health Insurance Research Database for the period between 1 January 2000 and 31 December 2013, to establish matched cohorts (14,109 with and 42,327 without metformin use) at a ratio of 1:3 by sex, age and index year.

We used a Cox regression hazard model to identify risk factors of sudden sensorineural hearing loss during 14 years of follow-up, and the results indicate that a significantly lower percentage of diabetes mellitus patients with metformin use (p = 0.033) developed sudden sensorineural hearing loss compared with those without metformin use (0.21%, 29/14,109 vs 0.32%, 136/42,327). After adjustment for age and other variables [adjusted hazard ratio: 0.630 (95% confidence interval: 0.422–0.941, p = 0.024)], this study also demonstrated that metformin use appeared to reduce the risk of developing sudden sensorineural hearing loss.

This study demonstrated an association between metformin use and lower incidence of sudden sensorineural hearing loss among patients with diabetes mellitus.