Incidence Rate and Prevalence of Systemic Sclerosis and Systemic Sclerosis-Associated Interstitial Lung Disease in Japan: Analysis Using Japanese Claims Databases

Abstract

Introduction: Systemic sclerosis (SSc) is a complex autoimmune disease with increased mortality, and interstitial lung disease (ILD) is a major cause of death. There are no recent epidemiological data on SSc and SSc-associated ILD (SSc-ILD) in Japan and little is known about how patients with these diseases are treated.

Methods: The incidence rate and prevalence of SSc and SSc-ILD in Japan were estimated using the Japanese Medical Data Centre (JMDC) database. The demographic and clinical characteristics of patients and the immunomodulatory medications they received were also assessed using JMDC and the Medical Data Vision (MDV) databases. All analyses were descriptive.

Results: The overall incidence rates of SSc and SSc-ILD per 100,000 person-years were 6.6 (95% confidence interval [CI] 6.2-7.1) and 1.9 (95% CI 1.6-2.1), respectively, and the overall prevalence per 100,000 persons was 37.0 (95% CI 35.6-38.5) and 13.9 (95% CI 13.0-14.8), respectively. ILD was the most common comorbidity in patients with SSc present in approximately 30% of patients (JMDC, 29.3%; MDV, 30.1%). The immunomodulatory medications prescribed were similar in patients with SSc and SSc-ILD, and each of the medications in this analysis was prescribed in less than 15% of patients.

Conclusion: We have demonstrated that estimates of prevalence and incidence rates of SSc and SSc-ILD in Japan are comparable to similar database studies conducted in the USA, using a medical claims database. Only a small proportion of patients were receiving immunomodulatory treatments, suggesting undertreatment in Japan. Incidence Rate and Prevalence of Systemic Sclerosis and Systemic Sclerosis-associated Interstitial Lung Disease in Japan: Analysis Using Japanese Claims Databases-A Video Abstract. (MP4 68892 KB).

Keywords: Epidemiology; Immunosuppressant; Interstitial lung disease; Scleroderma; Systemic sclerosis.

Fig. 1

Schematic of the study design. ^aIndex date varied depending on the date participants fulfilled eligibility criteria. SSc systemic sclerosis, SSc-ILD SSc-associated interstitial lung disease

Fig. 2

Comorbidities at baseline in a patients with SSc and b patients with SSc-ILD (JMDC and MDV). Comorbidities were defined by ICD10 MHLW2013. ILD: J84.x; Heart failure: I50.x; Digital ulcer/gangrene: L98.x; Pulmonary hypertension: I27.x; Arrhythmia: I44.x, I45.x, I47.x, I48.x, I49.x; Kidney failure: N17.x, N18.x, N19.x; Respiratory failure: J96.x; Pseudo-ileus: K56.x; Scleroderma renal crisis: M34.8; Pericarditis: I30.x, I31.x, I32.x; Cardiomyopathy: I42.x, I43.x. ICD International Classification of Disease, ILD interstitial lung disease, JMDC Japanese Medical Data Centre, MDV Medical Data Vision, SSc systemic sclerosis, SSc-ILD SSc-associated interstitial lung disease

Fig. 3

Incidence rates of selected disease outcomes among patients with SSc or SSc-ILD (prevalence cohort): JMDC and MDV databases. Incidence rates for ILD in patients with SSc-ILD are not shown as all the patients in this group were diagnosed with ILD. Death: disenrolment from the insurance system with a cause categorized as “death” in JMDC and I46.1, I46.9, R96, R98, R99 or discharge summary (FF1 data) in MDV. Other selected disease outcomes were defined by ICD10 MHLW2013. ILD: J84.x; Heart failure: I50.x; Digital ulcer/gangrene: L98.x; Pulmonary hypertension: I27.x; Arrhythmia: I44.x, I45.x, I47.x, I48.x, I49.x; Respiratory failure: J96.x; Kidney failure: N17.x, N18.x, N19.x; Scleroderma renal crisis: M34.8; Pseudo-ileus: K56.x; Pericarditis: I30.x, I31.x, I32.x; Cardiomyopathy: I42.x, I43.x. ICD International Classification of Disease, ILD interstitial lung disease, IR incidence rate, PY patient years, SSc systemic sclerosis, SSc-ILD SSc-associated ILD

Fig. 4

Medications to treat patients with SSc or SSc-ILD aged 20 years or more (prevalence cohort): a JMDC and b MDV databases. ABT abatacept, AZA azathioprine, CsA cyclosporine, CYC cyclophosphamide hydrate, HCQ hydroxychloroquine sulfate, MMF mycophenolate mofetil, MTX methotrexate, MZR mizoribine, RTX rituximab, SSc systemic sclerosis, SSc-ILD SSc-associated interstitial lung disease, Tac tacrolimus hydrate, TCZ tocilizumab, TNF tumour necrosis factor