Background/Purpose: Sporadic inclusion body myositis (sIBM) is a rare & debilitating muscle disease characterized by the slow progressive asymmetric weakness, atrophy of proximal & distal muscle, with symptoms generally developing ≥ 50 years of age. This study aimed to describe demographics & clinical profile of sIBM patients, to evaluate their healthcare resource utilization & economic cost compared to a matched general population cohort.

Methods: Using administrative claims data from the Truven MarketScan Commercial & Medicare supplemental database, the sIBM patient cohort included patients (≥50 years) with ≥2 outpatient diagnoses of sIBM ≥7 days apart or with ≥ 1 inpatient sIBM diagnosis identified between January 1, 2010 & December 31, 2012. The date of the first observed diagnosis of sIBM was defined as the index date; patients with ≥1 year continuous enrollment in medical insurance plans pre- & post-index were included. The control cohort was selected from patients without sIBM with ≥ 1 healthcare encounter between January 1, 2010 & December 31, 2012. Patients with diagnoses of congenital hereditary muscular dystrophy/ hereditary progressive muscular dystrophy were excluded. Control patients were matched to sIBM patients by age, gender, region, continuous enrollment of medical benefits in 1: 5 ratio & were assigned the same index date as the paired sIBM patients. Generalized Estimating Equation models with appropriate link functions & two parts models were conducted controlling for matching structure, to assess health care utilization & costs of sIBM patients in the follow up period compared to the control group, adjusting for baseline characteristics and healthcare resource utilization.

Results: 333 sIBM patients & 1,665 matched controls (66% male) with a mean age of 69 years (SD: 9.6) were included in the analysis. Charlson comorbidity index score was significantly higher (P<0.0001) in sIBM patients (Mean: 2.0 SD: 2.4) compared to controls (Mean: 1.2, SD: 1.9). 11.1% of sIBM patients reported pneumonia compared to 3.2% of the controls, while 22.5% of sIBM patients reported dsyphagia compared to 2.0% of the controls (P<0.0000). Falls requiring medical visit were reported by 8.1% of sIBM patients compared to 1.1% of the controls (P<0.0000). 26% of sIBM patients had an all-cause hospitalizations, 42% had an ER visits & 99% had an office visit compared to the control patients of 12%, 22%, and 95% (P<0.0002), respectively. Number of office visits were significantly higher in sIBM patients compared to control (mean [SD]): 11.4 [7.2] vs. 7.0 [6.3], P<0.0001). Adjusting for baseline characteristics, sIBM patients had higher risk of all-cause hospitalization, (OR: 1.89; 95% CI: 1.34–2.67), all-cause ER visits (OR: 1.94; 95% CI: 1.46–2.58), office visits (OR: 3.03; 95% CI: 0.88–10.49), & had higher healthcare cost (Mean difference: $19,389; 95% CI: 12,855–26,763) compared to the control group.

Conclusion: sIBM imposes a considerable economic burden in terms of increased healthcare resource used & associated costs compared to the matched general population. The major cost driver was outpatient costs.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/economic-burden-of-sporadic-inclusion-body-myositis-in-the-united-states-of-america-a-retrospective-cohort-study/