Type 2 diabetes and the risk of incident hearing loss

AIMS/HYPOTHESIS: Type 2 diabetes mellitus has been implicated as a risk factor for hearing loss, with possible mechanisms including microvascular disease, acoustic neuropathy or oxidative stress. A few small studies have examined the longitudinal association between type 2 diabetes and hearing loss, but larger studies are needed. Our objective was to examine whether type 2 diabetes (including diabetes duration) is associated with incident hearing loss in two prospective cohorts: Nurses’ Health Studies (NHS) I and II. METHODS: We conducted a longitudinal study of 139,909 women to examine the relationship between type 2 diabetes and the risk of self-reported incident hearing loss. A physician-diagnosis of diabetes was ascertained from biennial questionnaires. The primary outcome was hearing loss reported as moderate or worse in severity (categorised as a ‘moderate or severe’ hearing problem, or ‘moderate hearing trouble or deaf’) on questionnaires administered in 2012 in NHS I and 2009 or 2013 in NHS II. Cox proportional hazards regression was used to adjust for potential confounders. RESULTS: During >2.4 million person-years of follow-up, 664 cases of moderate or worse hearing loss were reported among those with type 2 diabetes and 10,022 cases among those without type 2 diabetes. Compared with women who did not have type 2 diabetes, those with type 2 diabetes were at higher risk for incident moderate or worse hearing loss (pooled multivariable-adjusted HR 1.16 [95% CI 1.07, 1.27]). Participants who had type 2 diabetes for ≥8 years had a higher risk of moderate or worse hearing loss compared with those without type 2 diabetes (pooled multivariable-adjusted HR 1.24 [95% CI 1.10, 1.40]). CONCLUSIONS/INTERPRETATION: In this large longitudinal study, type 2 diabetes was associated with a modestly higher risk of moderate or worse hearing loss. Furthermore, longer duration diabetes was associated with a higher risk of moderate or worse hearing loss.