Metformin lowers risk of hearing loss and mortality in type 2 diabetes

Aims: To assess the association between metformin use and the risk of sudden sensorineural hearing loss (SSNHL) in patients with Type 2 diabetes (T2D), a population at elevated risk for SSNHL.

Materials and methods: This cohort study utilized data from Taiwan's National Health Insurance Research Database, following T2D patients from 2008 to 202 database's baseline. Metformin use was defined as achieving ≥80% of the medication possession ratio (MPR) and ≥28 cumulative defined daily doses (cDDD) within three months. The control group included patients with ≥80% MPR from other antidiabetic agents, ensuring active treatment comparability. Propensity score matching was applied to balance covariates, while competing risk models accounted for mortality. Hazard ratios (HRs), incidence rates (IRs), and incidence rate ratios (IRRs) were calculated.

Results: Metformin users demonstrated a lower SSNHL incidence (IR: 11.48 per 10,000 person-years) compared to non-users (IR: 15.66 per 10,000 person-years), with an IRR of 0.73 (95% CI: 0.66-0.82; p < 0.0001). Adjusted HRs indicated a 27% reduction in SSNHL risk (HR: 0.73; 95% CI: 0.66-0.82). Higher cumulative doses (Q4: HR 0.36; 95% CI: 0.29-0.46) and daily doses ≥1 DDD (HR: 0.78; 95% CI: 0.69-0.87) were linked to further risk reductions. Metformin use was also associated with lower overall mortality.

Conclusions: Metformin use is associated with a dose-dependent reduction in SSNHL risk and lower mortality in T2D patients. The rigorous definitions of metformin exposure and an actively treated comparator group emphasize these findings, suggesting metformin's potential role in SSNHL prevention and improved survival.