Muscle strength, not muscle mass, determines the health-related quality of life in Indonesian women with systemic lupus erythematosus

OBJECTIVE: No study evaluated the impact of low muscle strength and mass on the Sarcopenia-related Quality of Life (SarQoL) in women with SLE. METHODS: This cross-sectional study recruited 145 women with SLE consecutively; muscle strength was measured with a calibrated Jamar handheld dynamometer, muscle mass was measured with appendicular muscle mass index (Tanita MC-780 MAP body impedance analyser) and health-related quality of life with SarQoL Questionnaire. The cut-off points for low muscle strength, low muscle mass and sarcopenia were derived from the Asian Working Group on Sarcopenia 2019. Statistical analysis was conducted with a t-test for mean difference, and logistic regression was used to evaluate for low muscle strength contributing factors. RESULTS: There was a significant difference in the mean total score of SarQoL in individuals with normal compared with low muscle strength (74.36 vs 64.85; mean difference 9.50; 95% CI 2.10 to 5.33; p<0.001). On the other hand, there was no difference in individuals with normal compared with low muscle mass (71.07 vs 70.79; mean difference 0.28; −5.18 to 5.74; p=0.91). After minimally adjusted with age, we found moderate-severe joint pain (B −9.280; p<0.001) and low muscle strength (B −6.979; p=0.001) to be independently associated with low mean SarQoL total score. CONCLUSION: There was a lower total SarQoL score in individuals with low muscle strength but not with low muscle mass.