Background/Purpose: Muscle weakness is common and contributes to physical disability in women with systemic lupus erythematosus (SLE). Recently, the Foundation for the National Institutes of Health Sarcopenia Project reported grip strength cutpoints that identified weakness associated with impaired mobility among women aged ≥ 65 years.   However, the ability of grip strength to identify SLE patients at increased risk of physical disability is unknown.  This study aims to test whether grip strength is associated with increased physical disability in women with SLE. 

Methods: Subjects were women in a longitudinal cohort with physician-documented SLE.  All measures were collected during an in-person research visit among a subset of the cohort.  Grip strength was measured with a handheld dynamometer.  Grip strength was classified as “weak” (<16kg), “intermediate” (16-20kg), and “normal” (>20kg).  Self-reported physical functioning was assessed using the SF-36 Physical Functioning subscale (range 0-100, mean 50, SD 10) and Valued Life Activities (VLA) Disability (range 0-3) surveys.  Higher SF-36 and lower VLA scores indicate higher functioning. Regression analyses controlling for age, SLE duration, prednisone use, SLE disease activity measured with the Systemic Lupus Activity Questionnaire (SLAQ), physical activity level measured by the International Physical Activity Questionnaire (IPAQ), and depressive symptoms measured by the Center for Epidemiological Studies Depression Scale (CES-D) modeled the effects of grip strength on SF-36 and VLA scores. 

Results: Of the 146 women, mean age was 48 (±12) years; duration of SLE was 16 (±9) years; SF-36 score was 40.9 (±11.4); VLA disability score was 0.80 (±0.55).  Fifteen women (10%) had “weak” grip strength, 31 (21%) “intermediate, 78 (53%) “normal”; and 22 (15%) were missing grip strength data.  In both unadjusted and adjusted models, having “weak” compared to “normal” grip strength was associated with significantly worse SF-36 and VLA scores (see Table 1).  In sensitivity analyses examining the effects of missing grip strength data and of excluding women aged ≥ 65 years (n=11), the overall trends were unchanged. 

Conclusion:  Grip weakness was common in our cohort of women with SLE, with a prevalence comparable to that of geriatric populations.  Grip weakness successfully identified women with increased physical disability even when adjusting for potential confounders such as disease activity and depression.  These findings underscore the high burden of muscle weakness among women with SLE, and they may suggest a clinical role for grip strength testing in identifying women with SLE at greatest risk of physical disability.  Further studies will need to examine the ability of grip strength to predict incident disability in SLE.

Table 1. Association between Grip Strength and Disability Scores#
	SF-36 Physical Functioning		Valued Life Activities
	Unadjusted	Adjusted	Unadjusted	Adjusted
Weak (<16kg)	-11.8 (-17.6, -6.1)***	-4.4 (-8.7, -0.1)*	0.68 (0.40, 0.96)***	0.31 (0.11, 0.51)**
Intermediate (16-20kg)	-7.5 (-11.8, -3.2)**	-3.2 (-6.3, 0.01)	0.29 (0.08, 0.50)**	0.08 (-0.06, 0.23)
Normal (>20kg)	ref.	ref.	ref.	ref.
#Values are regression beta coefficients (95% CI).  Grip strength cutpoints defined per Alley DE et al., J Gerontol A Biol Sci Med Sci 2014 May; 69(5):559–566.  *p<0.05, **p<0.01, ***p<0.001

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/grip-strength-identifies-increased-physical-disability-in-women-with-systemic-lupus-erythematosus/