Association between frequency of adding salt to foods and risk of hearing loss: A population-based cohort study using UK Biobank data.

Objectives: To evaluate the association between the frequency of adding salt to food and the risk of incident hearing loss.

Design: A prospective cohort study.

Setting And Participants: 492,168 UK Biobank participants aged 40-69 years who were free of hearing loss at baseline (2006-2010) and followed through 2023.

Measurements: Frequency of salt addition to foods was self-reported and categorized as "Never/Rarely," "Sometimes," "Usually," or "Always." Incident hearing loss was identified using ICD-10 codes H90 and H91. Cox proportional hazards models were applied to estimate hazard ratios (HRs) and 95% confidence intervals (CIs), adjusting for demographic, lifestyle, and medical confounders. Causal mediation analyses were conducted to investigate potential intermediating roles of systemic inflammation and vascular dysfunction.

Results: Over a mean follow-up of 11 years, 19,188 participants developed hearing loss. The incidence rate increased from 3.37 to 4.33 per 1,000 person-years across ascending salt use categories. Compared with the "Never/Rarely" group, the adjusted HR for the "Always" group was 1.23 (95% CI, 1.16-1.32), with a significant dose-response relationship (p for trend <0.001). Subgroup analyses showed stronger associations among younger participants, men, and individuals without diabetes or hypertension. Mediation analysis indicated that systemic inflammatory markers, particularly glycoprotein acetyls and CRP, significantly mediated part of the association, while blood pressure and arterial stiffness did not demonstrate a significant mediating effect.

Conclusions: Frequent addition of salt to food was associated with an increased risk of incident hearing loss in a dose-dependent manner. These findings suggest that salt intake may be a modifiable risk factor for hearing loss and implicate systemic inflammation as a potential biological pathway.