Work Ability and Employment in Rheumatoid Arthritis: A Cross-Sectional Study on the Role of Muscle Strength and Lower Extremity Function

Abstract

Objective. The aim of the present study was to assess the association between muscle strength, lower extremity function, employment status, and work ability in RA patients. Methods. One hundred seropositive RA outpatients of working age were included in this cross-sectional study. Employment status was assessed by interview and work ability by the Work Ability Index-Single Item Scale (WAS). Muscle strength was determined using dynamometer measurement of isometric hand grip and knee extensor strength. Lower extremity function was measured using the short physical performance battery (SPPB). Regression models estimate the association between unemployment, work ability and muscle strength, and lower extremity function, controlling for sociodemographic and disease-related factors. Results. Forty-one percent of the RA patients were not gainfully employed, and their median work ability had a good WAS value (7.00 [4.00-7.00]). Patients with better knee extensor strength (OR=1.07, 95% CI [1.02-1.12) and better physical performance (OR=1.71, 95% CI [1.18-2.49]) had a significantly better chance of gainful employment. The odds for hand grip strength remained significant when adjusted for sociodemographic (OR=1.5, 95% CI [1.00-1.09]), but not for disease-specific variables. Better hand grip strength (β=0.25, p=0.039) and better knee extensor strength (β=0.45, p=0.001) as well as better lower extremity function (SPPB) (β=0.51, p<0.001) remained significantly associated with work ability following adjustment for sociodemographic and disease-specific variables. Conclusions. The association of employment status and work ability with parameters of physical fitness suggests that improvement in muscle strength and lower extremity function may positively influence work ability and employment in individuals with RA.