title: The Association Between Serum 25-hydroxy Vitamin D Level and Upper Leg Strength in Patients with Knee Osteoarthritis: Results of the Amsterdam Osteoarthritis Cohort.
abstract: Vitamin D deficiency, which is common among elderly people, has been linked to muscle weakness. In patients with knee osteoarthritis (OA), the association between muscle strength and serum 25-hydroxy Vitamin D [25(OH)D] level has not been studied comprehensively. The aim of our study was to examine the association between serum 25(OH)D level and muscle strength in patients with knee OA.
  
  
  
  Data of the Amsterdam Osteoarthritis cohort from 319 participants with knee OA were used in a cross-sectional study. Serum 25(OH)D level (nmol/l) was measured by a competitive electrochemiluminescence method. Muscle strength (nm/kg) of the upper leg was measured isokinetically. Univariable and multivariable linear regression analyses were used to calculate the association between serum 25(OH)D level and muscle strength.
  
  
  
  Serum 25(OH)D level was significantly associated with muscle strength (B = 0.036, 95% CI 0.017-0.054, p < 0.001), adjusted for season of blood collection. After adding body mass index (BMI) to the model, this association was no longer significant (B = 0.011, 95% CI -0.007 to 0.029, p = 0.214). Alcohol consumption, number of comorbidities, and sex were subsequently added and changed the model slightly. Without BMI, this model showed a significant association between serum 25(OH)D level and muscle strength (B = 0.029, 95% CI 0.014-0.043, p < 0.001).
  
  
  
  The observed association between a low serum 25(OH)D level and muscle weakness in patients with knee OA is attenuated by BMI. Further studies are needed to explain the associations among Vitamin D level, muscle strength, and adiposity in patients with knee OA.
authors.affiliation: From the Amsterdam Rehabilitation Research Center/Reade; Department of Rehabilitation Medicine, and EMGO Institute for Health and Care Research, and Department of Epidemiology and Biostatistics, and Department of Psychiatry, VU University Medical Center; Reade, Department of Rheumatology, Amsterdam, the Netherlands.E. Koeckhoven, MSc, Amsterdam Rehabilitation Research Center/Reade; M. van der Leeden, PhD, Amsterdam Rehabilitation Research Center/Reade, and Department of Rehabilitation Medicine, and EMGO Institute for Health and Care Research, VU University Medical Center; L.D. Roorda, PhD, Amsterdam Rehabilitation Research Center/Reade; N.M. van Schoor, PhD, EMGO Institute for Health and Care Research, and Department of Epidemiology and Biostatistics, VU University Medical Center; P. Lips, PhD, Department of Internal Medicine/Endocrinology, VU University Medical Center; A. de Zwart, MSc, Amsterdam Rehabilitation Research Center/Reade; J. Dekker, PhD, Department of Rehabilitation Medicine, and EMGO Institute for Health and Care Research, and Department of Psychiatry, VU University Medical Center; M. van der Esch, PhD, Amsterdam Rehabilitation Research Center/Reade; W.F. Lems, PhD, Department of Rheumatology, VU University Medical Center, and Amsterdam Rehabilitation Research Center/Reade.
authors.forename: Esmee
authors.initials: E
authors.lastname: Koeckhoven
authors.affiliation: From the Amsterdam Rehabilitation Research Center/Reade; Department of Rehabilitation Medicine, and EMGO Institute for Health and Care Research, and Department of Epidemiology and Biostatistics, and Department of Psychiatry, VU University Medical Center; Reade, Department of Rheumatology, Amsterdam, the Netherlands.E. Koeckhoven, MSc, Amsterdam Rehabilitation Research Center/Reade; M. van der Leeden, PhD, Amsterdam Rehabilitation Research Center/Reade, and Department of Rehabilitation Medicine, and EMGO Institute for Health and Care Research, VU University Medical Center; L.D. Roorda, PhD, Amsterdam Rehabilitation Research Center/Reade; N.M. van Schoor, PhD, EMGO Institute for Health and Care Research, and Department of Epidemiology and Biostatistics, VU University Medical Center; P. Lips, PhD, Department of Internal Medicine/Endocrinology, VU University Medical Center; A. de Zwart, MSc, Amsterdam Rehabilitation Research Center/Reade; J. Dekker, PhD, Department of Rehabilitation Medicine, and EMGO Institute for Health and Care Research, and Department of Psychiatry, VU University Medical Center; M. van der Esch, PhD, Amsterdam Rehabilitation Research Center/Reade; W.F. Lems, PhD, Department of Rheumatology, VU University Medical Center, and Amsterdam Rehabilitation Research Center/Reade. m.vd.leeden@reade.nl.
authors.forename: Marike
authors.initials: M
authors.lastname: van der Leeden
authors.affiliation: From the Amsterdam Rehabilitation Research Center/Reade; Department of Rehabilitation Medicine, and EMGO Institute for Health and Care Research, and Department of Epidemiology and Biostatistics, and Department of Psychiatry, VU University Medical Center; Reade, Department of Rheumatology, Amsterdam, the Netherlands.E. Koeckhoven, MSc, Amsterdam Rehabilitation Research Center/Reade; M. van der Leeden, PhD, Amsterdam Rehabilitation Research Center/Reade, and Department of Rehabilitation Medicine, and EMGO Institute for Health and Care Research, VU University Medical Center; L.D. Roorda, PhD, Amsterdam Rehabilitation Research Center/Reade; N.M. van Schoor, PhD, EMGO Institute for Health and Care Research, and Department of Epidemiology and Biostatistics, VU University Medical Center; P. Lips, PhD, Department of Internal Medicine/Endocrinology, VU University Medical Center; A. de Zwart, MSc, Amsterdam Rehabilitation Research Center/Reade; J. Dekker, PhD, Department of Rehabilitation Medicine, and EMGO Institute for Health and Care Research, and Department of Psychiatry, VU University Medical Center; M. van der Esch, PhD, Amsterdam Rehabilitation Research Center/Reade; W.F. Lems, PhD, Department of Rheumatology, VU University Medical Center, and Amsterdam Rehabilitation Research Center/Reade.
authors.forename: Leo D
authors.initials: LD
authors.lastname: Roorda
authors.affiliation: From the Amsterdam Rehabilitation Research Center/Reade; Department of Rehabilitation Medicine, and EMGO Institute for Health and Care Research, and Department of Epidemiology and Biostatistics, and Department of Psychiatry, VU University Medical Center; Reade, Department of Rheumatology, Amsterdam, the Netherlands.E. Koeckhoven, MSc, Amsterdam Rehabilitation Research Center/Reade; M. van der Leeden, PhD, Amsterdam Rehabilitation Research Center/Reade, and Department of Rehabilitation Medicine, and EMGO Institute for Health and Care Research, VU University Medical Center; L.D. Roorda, PhD, Amsterdam Rehabilitation Research Center/Reade; N.M. van Schoor, PhD, EMGO Institute for Health and Care Research, and Department of Epidemiology and Biostatistics, VU University Medical Center; P. Lips, PhD, Department of Internal Medicine/Endocrinology, VU University Medical Center; A. de Zwart, MSc, Amsterdam Rehabilitation Research Center/Reade; J. Dekker, PhD, Department of Rehabilitation Medicine, and EMGO Institute for Health and Care Research, and Department of Psychiatry, VU University Medical Center; M. van der Esch, PhD, Amsterdam Rehabilitation Research Center/Reade; W.F. Lems, PhD, Department of Rheumatology, VU University Medical Center, and Amsterdam Rehabilitation Research Center/Reade.
authors.forename: Natasja M
authors.initials: NM
authors.lastname: van Schoor
authors.affiliation: From the Amsterdam Rehabilitation Research Center/Reade; Department of Rehabilitation Medicine, and EMGO Institute for Health and Care Research, and Department of Epidemiology and Biostatistics, and Department of Psychiatry, VU University Medical Center; Reade, Department of Rheumatology, Amsterdam, the Netherlands.E. Koeckhoven, MSc, Amsterdam Rehabilitation Research Center/Reade; M. van der Leeden, PhD, Amsterdam Rehabilitation Research Center/Reade, and Department of Rehabilitation Medicine, and EMGO Institute for Health and Care Research, VU University Medical Center; L.D. Roorda, PhD, Amsterdam Rehabilitation Research Center/Reade; N.M. van Schoor, PhD, EMGO Institute for Health and Care Research, and Department of Epidemiology and Biostatistics, VU University Medical Center; P. Lips, PhD, Department of Internal Medicine/Endocrinology, VU University Medical Center; A. de Zwart, MSc, Amsterdam Rehabilitation Research Center/Reade; J. Dekker, PhD, Department of Rehabilitation Medicine, and EMGO Institute for Health and Care Research, and Department of Psychiatry, VU University Medical Center; M. van der Esch, PhD, Amsterdam Rehabilitation Research Center/Reade; W.F. Lems, PhD, Department of Rheumatology, VU University Medical Center, and Amsterdam Rehabilitation Research Center/Reade.
authors.forename: Paul
authors.initials: P
authors.lastname: Lips
authors.affiliation: From the Amsterdam Rehabilitation Research Center/Reade; Department of Rehabilitation Medicine, and EMGO Institute for Health and Care Research, and Department of Epidemiology and Biostatistics, and Department of Psychiatry, VU University Medical Center; Reade, Department of Rheumatology, Amsterdam, the Netherlands.E. Koeckhoven, MSc, Amsterdam Rehabilitation Research Center/Reade; M. van der Leeden, PhD, Amsterdam Rehabilitation Research Center/Reade, and Department of Rehabilitation Medicine, and EMGO Institute for Health and Care Research, VU University Medical Center; L.D. Roorda, PhD, Amsterdam Rehabilitation Research Center/Reade; N.M. van Schoor, PhD, EMGO Institute for Health and Care Research, and Department of Epidemiology and Biostatistics, VU University Medical Center; P. Lips, PhD, Department of Internal Medicine/Endocrinology, VU University Medical Center; A. de Zwart, MSc, Amsterdam Rehabilitation Research Center/Reade; J. Dekker, PhD, Department of Rehabilitation Medicine, and EMGO Institute for Health and Care Research, and Department of Psychiatry, VU University Medical Center; M. van der Esch, PhD, Amsterdam Rehabilitation Research Center/Reade; W.F. Lems, PhD, Department of Rheumatology, VU University Medical Center, and Amsterdam Rehabilitation Research Center/Reade.
authors.forename: Arjan
authors.initials: A
authors.lastname: de Zwart
authors.affiliation: From the Amsterdam Rehabilitation Research Center/Reade; Department of Rehabilitation Medicine, and EMGO Institute for Health and Care Research, and Department of Epidemiology and Biostatistics, and Department of Psychiatry, VU University Medical Center; Reade, Department of Rheumatology, Amsterdam, the Netherlands.E. Koeckhoven, MSc, Amsterdam Rehabilitation Research Center/Reade; M. van der Leeden, PhD, Amsterdam Rehabilitation Research Center/Reade, and Department of Rehabilitation Medicine, and EMGO Institute for Health and Care Research, VU University Medical Center; L.D. Roorda, PhD, Amsterdam Rehabilitation Research Center/Reade; N.M. van Schoor, PhD, EMGO Institute for Health and Care Research, and Department of Epidemiology and Biostatistics, VU University Medical Center; P. Lips, PhD, Department of Internal Medicine/Endocrinology, VU University Medical Center; A. de Zwart, MSc, Amsterdam Rehabilitation Research Center/Reade; J. Dekker, PhD, Department of Rehabilitation Medicine, and EMGO Institute for Health and Care Research, and Department of Psychiatry, VU University Medical Center; M. van der Esch, PhD, Amsterdam Rehabilitation Research Center/Reade; W.F. Lems, PhD, Department of Rheumatology, VU University Medical Center, and Amsterdam Rehabilitation Research Center/Reade.
authors.forename: Joost
authors.initials: J
authors.lastname: Dekker
authors.affiliation: From the Amsterdam Rehabilitation Research Center/Reade; Department of Rehabilitation Medicine, and EMGO Institute for Health and Care Research, and Department of Epidemiology and Biostatistics, and Department of Psychiatry, VU University Medical Center; Reade, Department of Rheumatology, Amsterdam, the Netherlands.E. Koeckhoven, MSc, Amsterdam Rehabilitation Research Center/Reade; M. van der Leeden, PhD, Amsterdam Rehabilitation Research Center/Reade, and Department of Rehabilitation Medicine, and EMGO Institute for Health and Care Research, VU University Medical Center; L.D. Roorda, PhD, Amsterdam Rehabilitation Research Center/Reade; N.M. van Schoor, PhD, EMGO Institute for Health and Care Research, and Department of Epidemiology and Biostatistics, VU University Medical Center; P. Lips, PhD, Department of Internal Medicine/Endocrinology, VU University Medical Center; A. de Zwart, MSc, Amsterdam Rehabilitation Research Center/Reade; J. Dekker, PhD, Department of Rehabilitation Medicine, and EMGO Institute for Health and Care Research, and Department of Psychiatry, VU University Medical Center; M. van der Esch, PhD, Amsterdam Rehabilitation Research Center/Reade; W.F. Lems, PhD, Department of Rheumatology, VU University Medical Center, and Amsterdam Rehabilitation Research Center/Reade.
authors.forename: Martin
authors.initials: M
authors.lastname: van der Esch
authors.affiliation: From the Amsterdam Rehabilitation Research Center/Reade; Department of Rehabilitation Medicine, and EMGO Institute for Health and Care Research, and Department of Epidemiology and Biostatistics, and Department of Psychiatry, VU University Medical Center; Reade, Department of Rheumatology, Amsterdam, the Netherlands.E. Koeckhoven, MSc, Amsterdam Rehabilitation Research Center/Reade; M. van der Leeden, PhD, Amsterdam Rehabilitation Research Center/Reade, and Department of Rehabilitation Medicine, and EMGO Institute for Health and Care Research, VU University Medical Center; L.D. Roorda, PhD, Amsterdam Rehabilitation Research Center/Reade; N.M. van Schoor, PhD, EMGO Institute for Health and Care Research, and Department of Epidemiology and Biostatistics, VU University Medical Center; P. Lips, PhD, Department of Internal Medicine/Endocrinology, VU University Medical Center; A. de Zwart, MSc, Amsterdam Rehabilitation Research Center/Reade; J. Dekker, PhD, Department of Rehabilitation Medicine, and EMGO Institute for Health and Care Research, and Department of Psychiatry, VU University Medical Center; M. van der Esch, PhD, Amsterdam Rehabilitation Research Center/Reade; W.F. Lems, PhD, Department of Rheumatology, VU University Medical Center, and Amsterdam Rehabilitation Research Center/Reade.
authors.forename: Willem F
authors.initials: WF
authors.lastname: Lems
mesh_terms: D000328:Adult; D000368:Aged; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology*; D009426:Netherlands; D020370:Osteoarthritis, Knee / Q000097:blood* / Q000503:physiopathology; D013848:Thigh / Q000503:physiopathology*; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D
keywords: BODY MASS INDEX; MUSCLE STRENGTH; OSTEOARTHRITIS; VITAMIN D