Prevalence of systemic lupus erythematosus and age-stratified treatment trends in the Japanese population: a cross-sectional study based on the National Database of Health Insurance Claims.

Objectives: To investigate the prevalence of systemic lupus erythematosus in Japan and explore its treatment regimens in different age groups.

Methods: We identified patients with systemic lupus erythematosus from the national database of anonymized health insurance-related information; they had disease names associated with systemic lupus erythematosus and were treated with glucocorticoids, hydroxychloroquine, or immunosuppressants. These data were used to investigate disease prevalence and profiles in Japan.

Results: Of 74,277 patients with systemic lupus erythematosus, 12,816 were men (16.6%) and 61,961 were women (83.4%). Oral glucocorticoids were administered to 89.1% of patients and hydroxychloroquine to 21.4%. Regarding immunosuppressants, mycophenolate mofetil was prescribed for 49.2% of patients aged ≤14 years and tacrolimus for 35.5% of those aged 20-39 years; these rates were higher than those observed in other age groups.

Conclusions: The high proportion of patients receiving treatment for comorbidities may be partially explained by the high rate of glucocorticoid use, as approval of hydroxychloroquine for the treatment of systemic lupus erythematosus was delayed in Japan. This is the first study to ascertain the prevalence of systemic lupus erythematosus and its treatment status in Japan using the national database, thus providing useful basic data to improve management of the disease.