The lower extremity strength or weakness of women with systemic lupus erythematosus was predictive of later higher or lower functional status but was unrelated to grip strength, according to research published in Arthritis Care and Research.
A total of 146 women with systemic lupus erythematosus (SLE) were included in the analysis. Patients who resided in the San Bay area and were enrolled in the University of California, San Francisco (UCSF) Lupus Outcomes Study (LOS) were included. Demographic information was collected, and patients completed assessments, including the Short Physical Performance Battery (SPPB), Systemic Lupus Activity Questionnaire (SLAQ) and International Physical Activity Questionnaire (IPAQ) at baseline and follow-up.
Body composition and muscle distribution were assessed in the CRC using a Lunar Prodigy (GE Healthcare) whole-body, dual-energy, X-ray absorptiometry (DXA) scan. Knee torque was measured to assess lower body strength using a Biodex unit (Biodex Medical Systems) to measure peak isokinetic torques of knee extension and exion at 120 per second with adjustments for body weight.
The mean peak knee torque extension was 44.5 Nm and flexion was 29.9 Nm at baseline. The mean grip strength was 22.7 Nm and the mean SPPB score was 8.8 at baseline. The knee torque assessment was not completed by 24 patients and 24 patients did not complete the baseline grip assessment, seven did not complete either test.
Analysis revealed that a statistically significant association was seen between baseline knee torque and changes in SPPB scores, but not with grip scores, over an average of 2.4 years of follow-up. As an example, the researchers wrote that a 10-Nm increase in knee flexion peak torque from baseline was predictive of a 0.84-point increase in SBBP score at follow-up without any changes in covariates. Inversely, a decrease of 10 Nm was predictive of a decrease in SPPB score by 0.84 points.
“We observed that, among adult women with SLE, reduced lower extremity muscle strength predicted subsequent declines in physical function even when adjusting for covariates,” the researchers wrote. “In addition, we demonstrated that the weakest women are the ones at increased risk of future declines.” – by Shirley Pulawski
Disclosure: The researchers report no relevant financial disclosures.