P.14.16 Longitudinal changes in strength and functional outcomes in sporadic inclusion body myositis

Sporadic inclusion body myositis (sIBM) is the most common inflammatory myopathy in persons over the age of 50. Few studies have been completed to describe the natural history of the disease with both strength and functional outcome measures. 100 subjects were characterized in our initial study and 55 (43 male, 12 female; age range: 46–85 years; mean age: 66.8  ± 8.4 years) returned for longitudinal strength and functional outcomes testing. The average length of time between visits was 17.7 months (SD ± 7 mos.; range 1.1 months to 2.3 years). 5 subjects did not return because they were no longer ambulatory, 5 were enrolled in a clinical trial, 4 were lost to follow up, and the remaining 31 were unable to travel to Ohio during the testing period. Subjects reported falling up to 52 times per year, or weekly (mean = 5.4 ± 8.6 falls per year). Knee extension declined an average of 2% per month and knee flexion by 1.1% per month. Distance walked in 2 min decreased by 1.2 meters per month in this sample. The IBM functional rating scale and the PROMIS Health assessment questionnaire both captured patient perception of a decline in function (IBMFRS 0.32 points per month; PROMIS 1.1 points per month). Prediction models and rates of decline are also presented for walking distance, ability to get out of a chair and to step onto curbs. No significant difference in rate of change was found based on age of diagnosis. Understanding the rate of decline resulting from the natural history of a disease is essential to explaining the results of clinical trials. Expected rate of change over time can help patients and clinicians plan for the future needs and help researchers understand what changes are attributable to disease progression or to investigational agents. This is the most comprehensive longitudinal data reported in patients with sIBM to date.