Rheumatoid arthritis (RA) is an autoimmune disease. Sensorineural and conductive hearing loss have been reported in RA, but the results of most studies are not in agreement. The pathogenesis of the hearing loss is not clearly understood. The presence of sensorineural hearing loss was related to matrix metalloproteinase-3 (MMP-3). The aim of this study was to assess hearing loss in RA patients and to examine the correlation between plasma MMP-3 levels and hearing loss in such patients.
This is a cross-sectional and analytic research. Subjects consisted of 21 RA patients with hearing loss as a study group and 21 RA patients without hearing loss as controls. All patients were evaluated by pure tone audiometry and tympanometry. The amounts of plasma MMP-3 were determined using enzyme-linked immunosorbent assay. Pearson Chi-square test was used to determine the correlation of gender, age, disease duration, erythrocyte sedimentation rate, and platelet count of both groups. Independent t-test was used to assess equality of mean values at 250 to 8000 Hz hearing thresholds, pure tone mean values, air-bone gaps, and MMP-3 plasma levels of both groups.
This study found sensorineural (76.2%), conductive (14.3%), and mixed (9.5%) hearing loss. The most common degree of hearing loss was mild (66.7%). There was an increased incidence of As-type tympanogram in the study group (28.6%) and control group (47.6%). There were significant differences between both groups in mean hearing thresholds (p < 0.001), mean of air conduction thresholds at 1000 to 8000 Hz (p < 0.05), and mean of bone conduction thresholds in all frequencies (p < 0.05). The significant difference of mean MMP-3 levels was also found between the groups (p < 0.001).
Hearing loss is a common finding in RA. MMP-3 plasma contributed to degrade the incudomalleolar and incudostapedial joints and could damage the inner ear hair cells due to oxidative process in RA.