Age-related hearing impairment (HI) may occur as a result of reduced kidney function, researchers suggest. Researchers used serum concentration of cystatin C (CysC) as a biomarker for estimated glomerular filtration rate (eGFRCysC).

Hearing impairment (HI) is one of the most common conditions affecting older adults. Identification of factors associated with the development of HI may lead to ways to reduce the incidence of this condition.

Carla Schubert of the University of Wisconsin in Madison and colleagues analyzed data from a longitudinal population-based hearing loss study in Beaver Dam, Wisconsin. Participants without HI were examined at baseline (1993-1995) and serially for the next 20 years.

Researchers used serum concentration of cystatin C (CysC) as a biomarker for estimated glomerular filtration rate (eGFRCysC). In a cohort of 863 participants (mean age, 62; 69.4% women), serum CysC concentration was associated with an increased risk of developing HI (hazard ratio, 1.20) after adjustment for age and gender. 

After further adjustment for educational level, current smoking, waist circumference, and glycated hemoglobin, however, the association was no longer significant (HR, 1.11), the authors reported online in JAMA Otolaryngology-Head and Neck Surgery.

Low eGFRCysC (<60 mL/min/1.73 m2), consistent with moderate or worse chronic kidney disease, was significantly associated with the 20-year cumulative incidence of HI in both the age- and sex-adjusted model (HR, 1.70) and the multivariable-adjusted model (HR, 1.50).

Kidney function and hearing impairment

"These findings suggest that reduced kidney function is associated with an increased risk of developing HI but that CysC concentrations alone are not," the authors state. This study cannot determine causality," Schubert said.

"It is possible similar factors, such as microvascular damage, may affect both kidney health and hearing health. Health care providers should be aware that people with reduced kidney function may be more likely to develop HI," Schubert explained.

Dr. Edwin Monsell of Wayne State University School of Medicine in Detroit, Michigan, author of a related editorial, said, "The most effective and cost-effective action (for patients) is to get a general medical evaluation, which would include assessment of risk factors for cardiovascular disease and evidence for the presence of kidney disease."

"Cystatin C is not a screening test. It would be used to assess the degree of kidney disease and guide management if the screening tests are positive. Some primary care physicians might include the cystatin C if the there is a high suspicion for kidney disease, but there is no need if all the standard tests are normal," Monsell explained.