Muscle Functions in Polymyalgia Rheumatica and Giant-Cell Arteritis

Objectives: To find out whether and to what extent the muscle functions are impaired in polymyalgia rheumatica (PMR) patients in relation to duration, activity and treatment of the disease as well as any history of giant cell-arteritis (GCA). Methods: Comprehensive clinical examinations of PMR patients (N = 40) called to participate in a clinical rehabilitation trial included, among others, the polymyalgia rheumatica disease activity score (PMR-AS), cytokine profile, appendicular fat (aFMI) and muscle mass indices (aMMI) by dual X-ray absorbtiometry, mean hand grip strength of both hands (HGS) and force platform countermovement jump height (CJH). Results: Of the older PMR patients (57.2–80.9 years), five had a history of GCA. Neither aMMI nor aFMI was associated with age in these patients. The HGS correlated moderately with CJH (r = 0.629, P , 0.001). In multivariate regression analyses, old age (P = 0.003), low aMMI (P = 0.005), and high aFMI (P = 0.012) were independently associated with weak HGS, explaining 62.2% (R2 = 0.622) of its variation. Older age (P , 0.001), lower aMMI (P = 0.001) and higher aFMI (P , 0.001) also independently indicated lower CJH, explaining 75.3% (R2 = 0.753) of its variation. Muscle functions did not associate with disease characteristics of PMR or any history of GCA. Conclusions: Low muscle mass and adiposity are the most important determinants of impaired muscle function and are a target for prevention in older patients suffering from PMR.