Epidemiology of narcolepsy and idiopathic hypersomnia in Japan: A retrospective analysis of health insurance claims from the Japan Medical Data Center.

BACKGROUND

Estimation of prevalence and incidence of narcolepsy and idiopathic hypersomnia (IH) is challenging owing to symptomatic overlap, underdiagnosis, and misdiagnosis, and epidemiological data are lacking in Asian populations. We estimated the prevalence and incidence of narcolepsy and IH in Japan.

METHODS

The Japan Medical Data Center (JMDC) database includes healthcare claims data for employed individuals ≤74 years of age. Narcolepsy and IH cases were defined by ≥2 diagnosis codes within 12 months, or a multiple sleep latency test with ≥1 diagnosis code within 12 months. Estimated point-prevalences of diagnosed narcolepsy and IH were calculated for December 31, 2019. Incidences of narcolepsy and IH were estimated for the period January 1, 2014 to December 31, 2019.

RESULTS

Of 7,075,869 individuals enrolled in the database on December 31, 2019, 6,110,751 (86.4 %) had ≥12 months' continuous enrollment and were eligible for inclusion in the prevalence population. Age-sex standardized overall prevalences of narcolepsy and IH were 37.5 (95 % confidence intervals 35.9-39.1) and 7.7 (7.0-8.4) per 100,000 persons, respectively. Prevalence for both conditions peaked at age 20-29 years and declined with increasing age. Age-sex standardized overall incidences of narcolepsy and IH were 5.1 (4.8-5.4) and 1.2 (1.0-1.5) per 100,000 person-years, respectively. Narcolepsy and IH incidences peaked in the 10-19 and 20-29 years age groups then declined with increasing age.

CONCLUSIONS

This claims-based study provides updated estimates for the prevalence and incidence of narcolepsy in Japan, and the first estimates for prevalence and incidence of IH in Japan.