Exercise and outcome measures in patients with polymyositis and dermatomyositis

Abstract

Polymyositis (PM) and dermatomyositis (DM) are chronic idiopathic inflammatory myopathies (IIM) which are clinically characterized by symmetrical proximal muscle weakness, fatigue, myalgia and extra- muscular involvement. Muscle impairment is the most significant feature of PM and DM with characteristic infiltrates of mononuclear inflammatory cells in muscle biopsies, elevated inflammatory parameters in serum and characteristic EMG changes, which separate these disorders from neurologic disorders and also fibromyalgia.

First-line pharmaceutical treatment is oral corticosteroids together with other immunosuppressive agents. Despite an initial favorable response to treatment most patients develop sustained disability. Historically, these patients have been discouraged from active exercise due to a fear of exacerbated disease activity and little is known of the potential effects of exercise. The lack of valid and reliable outcome measures for patients with PM and DM for assessment of impairment, activity limitation and participation restriction limit the ability to evaluate different types of interventions in these patients.

The aim of this thesis was to develop and evaluate exercise regimens regarding both safety and efficacy for patients with chronic as well as active, recent onset PM and DM. Another objective was to develop disease-specific outcome measures and to evaluate their measurement properties.

An easy to moderate home exercise program was performed by patients with both chronic and active PM or DM five days a week for 12 weeks. An intensive resistive exercise program with a load of 10 voluntary repetition maximum (VRM) in five muscle groups was also performed by patients with chronic PM or DM three days a week for seven weeks. Assessments of disease activity and disability were conducted. A disease-specific, self-administrated questionnaire to assess activity limitation, the Myositis Activities Profile (MAP) was developed based on activities presented in the ICIDH-2 beta-2 draft. The Functional Index 2 (FI-2) was developed based on the original FI to assess impairment. These two outcome measures were evaluated for different aspects of validity and reliability.

The home exercise program could be safely employed in patients with both chronic and active disease, as no signs of increased muscle inflammation could be detected either by analyses of muscle biopsies, Magnetic resonance imaging (MRI) or CPK-levels. The patient groups improved with significantly reduced disability. The intensive resistive 7-week exercise program resulted in significantly reduced muscular impairment without any signs of increased disease activity as assessed by muscle biopsies and CPK-levels. Both the MAP and the FI-2 had satisfactory content validity, construct validity and reliability.

In summary, patients with chronic as well as active, recent onset PM or DM can perform individualized active exercise without increased muscle inflammation and with positive effects on muscle impairment, activity limitation and participation restriction. Active exercise should be included in the rehabilitation as an addition to pharmacological treatment. More research needs to be conducted to further minimize the patients' persisting impairment and activity limitation. The MAP and the FI-2 are valid, reliable and feasible instruments for assessing activity limitation and impairment and are also sensitive to change in these patients.