Estimated number and prevalence of patients with delayed endolymphatic hydrops in Japan: a nationwide survey.

Background: Delayed endolymphatic hydrops (DEH) is a rare disease, and the actual number of patients in Japan remains unknown.
Objective: To investigate the number and prevalence of patients with DEH in Japan.
Methods: In total, 781 departments of otolaryngology in Japan were selected for survey by stratified random sampling according to the total number of hospital beds. We sent questionnaires to the target departments and collected data regarding the number of patients with DEH who visited those departments in 2019.
Results: The overall response rate was 68.0% (531 departments). The estimate number of patients with DEH in Japan was 962, and the prevalence was calculated to be 0.8 per 100,000 population.
Conclusion: Patients with DEH were extremely rare in Japan.
Significance: This may be the first nationwide epidemiological study on the number and prevalence of patients with DEH in Japan or in the world.