Table 5. Summary of studies on vitamin D and hearing loss.

NHANES: National Health and Nutrition Examination Survey; SSNHL: Sudden sensorineural hearing loss

Article	Study design	Study characteristics	Main findings
Ghaznavi et al. [40]	Cross-sectional study	Sample size = 68 with 34 SSNHL cases and 34 normal individuals	73.5% of patients of SSNHL had low vitamin D levels and better treatment response was observed in patients with high vitamin D levels. Similarly, patients with sufficient vitamin D showed complete recovery compared to the rest
Szeto et al. [41]	Review of cross-sectional surveys obtained from NHANES	Sample size = 1123 with mean age = 76.4 ± 0.13	Age-related low-frequency and speech-frequency hearing loss are associated with vitamin D deficiency