Background/Purpose: Idiopathic inflammatory myopathies (IIM), such as dermatomyositis (DM), polymyositis (PM) and inclusion body myositis (IBM), are chronic multi-systemic inflammatory conditions. Substantial studies on health related quality of life (HRQOL) in IIM patients are lacking.

The objective of this study was to document the degree of HRQOL impairment in IIM patients.

Methods: Between December 2010 and July 2012, 1,715 patients who met probable Bohan and Peter criteria for myositis residing in the US and Canada registered for the MYOVISION registry study with The Myositis Association. HRQOL was ascertained via the SF-12v2^® Health Survey questionnaire. The SF12v2^®is a 12-item 4-week recall questionnaire that features two summary measures – the physical component summary [PCS] and the mental component summary [MCS].

This was an exploratory, cross-sectional descriptive study that examined the variation in HRQOL scores in relation to different patient and disease characteristics, and compared the scores of IIM patients to age-and-gender-matched normative U.S. general population and rheumatoid arthritis (RA) patients.

Bivariate analysis was conducted via t-tests to assess the difference in summary scores for each independent variable and a multiple linear regression analysis was performed using a backward elimination model.

Results: There were 702 DM, 481 PM, 465 IBM, as well as 59 adults with juvenile DM (JDM) and eight with juvenile PM (JPM) included in the study (70% females, 87% Caucasian). The median age at diagnosis and duration of disease were 49.9 and 9.2 years, respectively.

The mean summary scores of the SF-12v2^®were significantly lower (indicating reduced HRQOL) among the myositis population compared to the age-and-gender-matched normative population and the RA population (Table 1).

In a multiple linear regression (Table 2), older age, effect of disease on work, presence of another autoimmune disease, lung disease, joint involvement and use of multiple medications were all associated with lower PCS scores. Patients treated primarily by rheumatologists had a higher PCS score. The MCS score was lower with joint involvement and a negative effect of myositis on work.

Conclusion: In this largest study of patient reported outcomes in IIM to date, HRQOL was lower among IIM patients compared to the normal population and to RA patients. An association was found between multiple disease parameters and reduced HRQOL, mostly in the physical domain.