Clinical otosclerosis, prevalence estimates and spontaneous progress.

This retrospective study was performed in order to estimate the prevalence of clinical otosclerosis as a function of age and gender, characterize the hearing level in otosclerosis and describe the spontaneous progress of the disease as a function of age. Clinically based samples were obtained from an audiological department, including 556 subjects: n = 166 (30%) males and n = 390 (70%) females with a median age of 75 years (range 22-95 years) at the time of examination. A subdivision of the sample into 3 age-bands, 20-39 years (n = 39), 40-59 years (n = 78) and > or = 60 years (n = 439), was performed. The overall prevalence estimate of clinical otosclerosis in the area in question was 1.41/1,000 [95% confidence interval (CI) = 1.3-1.5/1,000] with an estimate of 0.9/1,000 (95% CI = 0.8-1.0/1,000) in males and 1.85/1,000 (95% CI = 1.7-2.1/1,000) in females, with an increase in the prevalence as a function of age from 0.22/1,000 (95% CI = 0.15-0.29/1,000) to 3.53/1,000 (95% CI = 3.2-3.86/1,000) in the elderly. The estimates should be considered underestimates, as not all clinical otosclerosis in the area was included. No significant differences in the better and worse ear hearing levels averaged across 0.5-4 kHz (BEHL/WEHL 0.5-4 kHz) were found as a function of gender, and in general the impairment in the BEHL 0.5-4 kHz was fairly moderate until the age of 60 years. In ears previously subjected to surgery a significantly better hearing level of median 63 dB (range 24-119 dB) was found than in the no-surgery ears, with a median hearing level of 71 dB (range 5-120 dB). An estimate of the progress showed an increment in the hearing level in the elderly > or = 60 years of 30 dB over 30 years in non-operated ears, fairly similar to the 40 dB progress in operated ears. It was concluded that a significantly higher prevalence of clinical otosclerosis is present in females than in males, that the overall hearing level in otosclerosis is fairly moderate until the age of 60 years, and that previously operated ears have significantly better hearing than non-operated ears.