Biomarkers of Systemic Inflammation and Risk of Incident Hearing Loss

BACKGROUND: Chronic inflammation may lead to cochlear damage, and the only longitudinal study that examined biomarkers of systemic inflammation and risk of hearing loss found an association with a single biomarker in individuals <60 years of age. The purpose of our study was to determine whether plasma inflammatory markers are associated with incident hearing loss in two large prospective cohorts, Nurses' Health Studies (NHS) I and II. METHODS: We examined the independent associations between plasma levels of markers of systemic inflammation (C-reactive protein [CRP], interleukin-6 [IL-6], and soluble tumor necrosis factor receptor 2 [TNFR-2]) and self-reported hearing loss. The participants in NHS I (n = 6194 women) were 42 to 69 years of age at the start of the analysis in 1990, while the participants in NHS II (n = 2885 women) were 32 to 53 years in 1995. After excluding women with self-reported hearing loss before the time of blood-draw, incident cases of hearing loss were defined as those women who reported hearing loss on questionnaires administered in 2012 in NHS I and 2009 or 2013 in NHS II. The primary outcome was hearing loss that was reported as moderate or worse in severity, pooled across the NHS I and NHS II cohorts. We also examined the pooled multivariable-adjusted hazard ratios for mild or worse hearing loss. Cox proportional hazards regression was used to adjust for potential confounders. RESULTS: At baseline, women ranged from 42 to 69 years of age in NHS I and 32 to 53 years of age in NHS II. Among the NHS I and II women with measured plasma CRP, there were 628 incident cases of moderate or worse hearing loss during 100,277 person-years of follow-up. There was no significant association between the plasma levels of any of the three inflammatory markers and incident moderate or worse hearing loss (multivariable-adjusted pooled p trend for CRP = 0.33; p trend IL-6 = 0.54; p trend TNFR-2 = 0.70). There was also no significant relation between inflammatory marker levels and mild or worse hearing loss. While there was no significant effect modification by age for CRP or IL-6 in NHS I, there was a statistically significant higher risk of moderate or worse hearing loss (p interaction = 0.02) as well as mild or worse hearing loss (p interaction = 0.004) in women ≥60 years of age who had higher plasma TNFR-2 levels. CONCLUSIONS: Overall, there was no significant association between plasma markers of inflammation and risk of hearing loss.