Correlation between muscle strength and physical function in women with systemic lupus erythematosus

The authors analyzed the correlation between muscle strength and physical function in women with systemic lupus erythematosus (SLE- a disease of the immune system). 

In SLE, the immune system mistakenly attacks normal, healthy tissues. SLE can affect the skin, joints, kidney, brain and other organs. There have been reports of decreased physical function in patients with SLE. However not much is known about the correlation between muscle strength and physical function in adult women with SLE. Further research is needed in this aspect. 

The authors aimed to examine if decreases in muscle strength in the upper (shoulder, arm, wrist and hand) and lower extremities (hip, thigh, leg, ankle and foot) affect physical function in adult women with SLE.

146 women with SLE participated in this study. The average time between the start of evaluation (baseline) and follow-up was 2.5 years. Upper extremity muscle strength was assessed by hand grip strength. Lower extremity muscle strength was assessed by knee torque (how well a patient can extend or bend the knee). Physical function and performance of lower extremities were assessed by a group of tests known as Short Physical Performance Battery (SPPB).

Based on SPPB, patients who had reduced muscle strength (knee torque) in their lower extremities experienced a decline in physical function after 2 years. There was no correlation between grip strength and physical function. Women who had reduced muscle strength at baseline had worse SPPB scores at follow up.The association between reduced muscle strength and reduced physical function in the future was greatest among the weakest women.

The authors concluded that reduction in muscle strength in the lower extremities predicted a decrease in physical function in adult women with SLE. They also suggested that appropriate therapy should be provided to preserve the muscle strength in SLE.