Nationwide epidemiology of retinitis pigmentosa in Japan, 2011-2020: a population-based cohort study

Retinitis pigmentosa (RP) is an inherited retinal disorder with limited contemporary national epidemiological data. This study aimed to describe the nationwide epidemiology of RP in Japan using a comprehensive national health insurance claims database.

This population-based longitudinal cohort study included approximately 126 million individuals covered by Japan's universal health coverage system. Data from the National Database of Health Insurance Claims from 2011 to 2020 were analysed. Patients with RP were identified as those who either had a confirmed RP diagnosis on electroretinography or had a confirmed RP diagnosis and received RP-specific treatment (e.g., helenien or vitamin A). Prevalence and incidence rates were calculated, and age-standardised rates were derived using the World Health Organization standard world population. Regional differences, mortality, and age at cataract surgery were also assessed.

As of October 1, 2020, 52,964 RP cases were identified, corresponding to a prevalence of 42.0 per 100,000 persons (approximately 1:2,400). The incidence rate was 2.52 per 100,000 person-years. Incidence was higher in southwestern Japan, particularly Kyushu and Shikoku, and lower in northern regions. The mean age at death was 81.7 ± 10.9 years. The mean age at cataract surgery was 68.6 ± 11.6 years.

This nationwide population-based study provides updated epidemiological data on RP in Japan, revealing higher prevalence than previously reported, geographic variation, and earlier age at the time of cataract surgery. These findings may inform clinical management, healthcare planning, and future research and clinical trials in inherited retinal diseases.