Schubert CR, et al. - Authors probed the relationship between cystatin C, both as an independent biomarker and as a marker of kidney function, and the 20-year incidence of hearing impairment (HI). They noted the association of reduced kidney function as estimated using cystatin C, but not cystatin C alone with the 20-year cumulative incidence of HI, thereby, indicating that some age-related HI could occur in conjunction with or as the result of reduced kidney function.

Methods

• Experts obtained the data from the Epidemiology of Hearing Loss Study (EHLS), a longitudinal, population-based study in Beaver Dam, Wisconsin.
• In 1993, baseline examinations began and continued through 1995, and participants were examined approximately every 5 years, with the most recent examination phase completed in 2015.
• They included the EHLS participants with serum cystatin C concentration data and without HI at the baseline examination in this study.
• For 20 years, participants without HI were followed up for incident HI (pure-tone average of hearing thresholds at 0.5, 1, 2, and 4 kHz >25 dB hearing level in either ear).
• Researchers analyzed cystatin C as a biomarker (concentration) and used it to determine estimated glomerular filtration rate (eGFR_CysC).
• To analyze the association between cystatin C concentration and eGFR_CysC and the 20-year cumulative incidence of HI, discrete-time Cox proportional hazards regression models were used.

Results

• As per the data, there were 863 participants aged 48 to 86 years with cystatin C data and without HI at baseline.
• Findings suggested that out of these, 599 (69.4%) were women.
• Results demonstrated that cystatin C was related to an increased risk of developing HI (hazard ratio [HR], 1.20; 95% CI, 1.07-1.34 per 0.2-mg/L increase in cystatin C concentration) in models adjusted for age and sex, but the estimate was attenuated after further adjusting for educational level, current smoking, waist circumference, and glycated hemoglobin (HR, 1.11; 95% CI, 0.98-1.27 per 0.2-mg/L increase in cystatin C concentration).
• Experts noted a significant association of low eGFR_CysC with the 20-year cumulative incidence of HI in both the age- and sex-adjusted model (HR, 1.70; 95% CI, 1.16-2.48; <60 vs ≥60 mL/min/1.73 m2) and the multivariable-adjusted model (HR, 1.50; 95% CI, 1.02-2.22; <60 vs ≥60 mL/min/1.73 m2).