title: Muscle Strength and Changes in Physical Function in Women With Systemic Lupus Erythematosus.
abstract: OBJECTIVE
  Cross-sectional studies have observed that muscle weakness is associated with worse physical function among women with systemic lupus erythematosus (SLE). The present study examines whether reduced upper and lower extremity muscle strength predict declines in function over time among adult women with SLE.
  
  
  METHODS
  One hundred forty-six women from a longitudinal SLE cohort participated in the study. All measures were collected during in-person research visits approximately 2 years apart. Upper extremity muscle strength was assessed by grip strength. Lower extremity muscle strength was assessed by peak knee torque of extension and flexion. Physical function was assessed using the Short Physical Performance Battery (SPPB). Regression analyses modeled associations of baseline upper and lower extremity muscle strength with followup SPPB scores controlling for baseline SPPB, age, SLE duration, SLE disease activity (Systemic Lupus Activity Questionnaire), physical activity level, prednisone use, body composition, and depression. Secondary analyses tested whether associations of baseline muscle strength with followup in SPPB scores differed between intervals of varying baseline muscle strength.
  
  
  RESULTS
  Lower extremity muscle strength strongly predicted changes over 2 years in physical function even when controlling for covariates. The association of reduced lower extremity muscle strength with reduced physical function in the future was greatest among the weakest women.
  
  
  CONCLUSIONS
  Reduced lower extremity muscle strength predicted clinically significant declines in physical function, especially among the weakest women. Future studies should test whether therapies that promote preservation of lower extremity muscle strength may prevent declines in function among women with SLE.
authors.affiliation: University of California, San Francisco.
authors.forename: James S
authors.initials: JS
authors.lastname: Andrews
authors.affiliation: University of California, San Francisco.
authors.forename: Laura
authors.initials: L
authors.lastname: Trupin
authors.affiliation: University of California, San Francisco, and VA Medical Center, San Francisco, California.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Schmajuk
authors.affiliation: Portland VA Medical Center and Oregon Health and Science University, Portland.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Barton
authors.affiliation: University of California, San Francisco.
authors.forename: Mary
authors.initials: M
authors.lastname: Margaretten
authors.affiliation: University of California, San Francisco.
authors.forename: Jinoos
authors.initials: J
authors.lastname: Yazdany
authors.affiliation: University of California, San Francisco.
authors.forename: Edward H
authors.initials: EH
authors.lastname: Yelin
authors.affiliation: University of California, San Francisco.
authors.forename: Patricia P
authors.initials: PP
authors.lastname: Katz
mesh_terms: D000328:Adult; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000503:physiopathology*; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology*; D018908:Muscle Weakness / Q000503:physiopathology