PhD student Division of Biostatistics, Tohoku University Graduate School of Medicine, Japan
Background: In Japan, narcolepsy is not currently covered by a medical expense assistance program, and the people living with narcolepsy have been criticizing the current situation. However, reports about economic burden (direct + indirect) and comorbidity that would provide support for coverage are apparently limited in Japan.
Objectives: The study objectives were to reveal the burden of narcolepsy from the perspectives of direct medical cost and comorbidity using a health claims database, and also to compare to schizophrenia/ ulcerative colitis as benchmarks. These diseases are currently covered by the medical expense assistance programs in Japan.
Methods: Patients diagnosed with narcolepsy (≥1 ICD-10code [G47.4]) were identified from April 2017 to March 2022 using employment-based health insurance claims data compiled by JMDC Inc. Patients with schizophrenia (≥2 ICD-10code [F20]) or with ulcerative colitis (≥2 ICD-10code [K51]) were 1:4/ 1:1 matched for age, sex, insurance status, and observation period. Direct medical cost (including inpatient, outpatient, and medication) and specific comorbidities were analyzed. The comorbidity items were pre-specified and captured regardless of the context to narcolepsy or benchmark diseases. The 95% confidence intervals (CI) for differences of two diseases were calculated by bootstrapping (direct medical cost) or conditional logistic regression models (comorbidity).
Results: We identified 4,594 patients with narcolepsy (sex; 58.7% males, age; 35.2 ± 12.7 years), 18,376 patients with schizophrenia (58.7%, 35.8 ± 12.0), and 4,594 patients with ulcerative colitis (58.7%, 36.7 ± 11.2). Overall annual direct medical costs per person were 349,188 JPY (narcolepsy). The differences between narcolepsy and schizophrenia/ ulcerative colitis were -83,194 JPY (95%CI; -103,995 JPY – -59,618 JPY)/ -149,044 JPY (-177,755 JPY – -117,823 JPY). In terms of comorbidities, sleep apnea syndrome (odds ratio; 6.16, 95% CI; 5.48 – 6.92), REM sleep behavior disorder (4.34, 2.92 – 6.45), and stroke (2.14, 1.76 – 2.61) were more prevalent in narcolepsy than in schizophrenia. In contrast, insomnia (0.33, 0.30 – 0.35), developmental disorders (0.35, 0.29 – 0.43), and depression (0.38, 0.35 – 0.41) were less prevalent in narcolepsy than in schizophrenia. All above comorbidities were more prevalent in narcolepsy than in ulcerative colitis.
Conclusions: The narcolepsy cost was about three times higher than the national medical expenses for people aged 15–44 years in 2020 (122,000 JPY). The patients were also likely to have diseases affecting the burden. These findings should help future discussion on the medical expense assistance program for narcolepsy. Further research is needed to show the indirect economic burden to clarify the burden.
