In-patient comorbidities in inclusion body myositis: a United States national in-patient sample-based study

Inclusion body myositis (IBM) is the most common idiopathic inflammatory myopathy (IIM) above the age of 50 with a distinct clinical phenotype of progressive, painless, asymmetric weakness predominantly involving the long finger flexors and quadriceps. In this study, we compared comorbidities in IBM with other IIMs (i.e., dermatomyositis (DM) and polymyositis (PM)) from the United States National Inpatient Sample Database.

We identified patients with a primary diagnosis of IBM or IIM from the National Inpatient Sample (NIS) from 2012 to 2018. We then compared the rate of common inpatient comorbidities between the IBM and IIM.

There were 18,819 admissions for patients with either IBM or IIM. IBM patients were older (72.9±10.7 years vs. 59.3±18.4 years for IIM, p<0.001), predominantly men (65.0% vs. 31.2% for IIM, p<0.001), and White Caucasians (82.5% vs. 58.4% for IIM, p<0.001). IBM patients had significantly more frequent events of aspiration pneumonia, atrial fibrillation, falls, and sepsis. The rate of PEG tube placement was also significantly higher. When performing multivariable logistic regression, we found that IBM is a risk factor for aspiration pneumonia (OR 3.03), PEG tube placement (OR 2.91), falls (OR 2.05), and sepsis (OR 1.30) but not for significant cardiovascular events.

IBM increases a patient's risk for dysphagia, falls, and infection as compared to other IIM patients. Further population-based studies are warranted to better elucidate the impact of these comorbidities in patients with IBM.