Vitamin D Deficiency as a Risk Factor for Onset and Recurrence of Sudden Sensorineural Hearing Loss: A Prospective Cohort Study With Age-Specific Analysis.

The link between Vitamin D (Vit D) deficiency and sudden sensorineural hearing loss (SSNHL), especially regarding recurrence and age-related disparities, remains unclear. Recurrence and age-specific risks of SSNHL are under addressed, limiting preventive strategies. This study investigated if Vit D deficiency increases SSNHL onset and recurrence risks, with a focus on age-specific associations. In this prospective cohort study, 80 adult SSNHL patients and 60 matched controls were enrolled. All patients received standard therapy. Baseline serum 25(OH)D was measured, Vit D deficiency or insufficient patients were randomized in a single-blind manner to receive 3-month Vit D supplementation. We monitored Vit D levels, hearing recovery (pure-tone audiometry at 10 days and 3 months), recurrence, and associated symptoms. Vit D deficiency was more prevalent in SSNHL patients than controls (38.8% vs. 10.0%, p = 0.000). Recurrent SSNHL patients had significantly lower Vit D levels (18.4 ± 4.1 ng/mL) than first-onset patients (24.9 ± 9.7 ng/mL). The highest deficiency rate (60.0%) was in patients under 30 years. Multivariate analysis identified audiometric subtype, not Vit D status, as an independent outcome predictor. Vit D supplementation did not significantly improve recovery rates (75.7% vs. 68.2%) or alleviate symptoms. Vit D deficiency is a significant, modifiable risk factor for SSNHL onset and recurrence, with the strongest association in patients under 30 years old. However, short-term Vit D supplementation initiated after SSNHL diagnosis failed to improve clinical outcomes, underscoring that long-term maintenance of adequate Vit D levels, rather than acute post-symptom intervention, may be critical for reducing SSNHL risk in high-risk populations.