Original Article Bioimpedance vector analysis as a measure of muscle function Kristina Norman a , Matthias Pirlich a, * , Janice Sorensen b, c , Pia Christensen b, c , Martin Kemps a , Tatjana Schu ¨ tz a , Herbert Lochs a , Jens Kondrup b, c a Charite´-Universita ¨tsmedizin Berlin Campus Mitte, Department of Gastroenterology, Berlin, Germany b Department of Human Nutrition, Royal Veterinary and Agricultural University, Frederiksberg, Denmark c Nutrition Unit 5711, Rigshospitalet, 2100 Copenhagen, Denmark article info Article history: Received 3 April 2008 Accepted 6 November 2008 Keywords: Bioelectrical impedance vector analysis Hand grip strength Tissue mass Cell integrity Altered electric tissue properties Functionality summary Introduction: The impedance vector produced by an alternating current in the bioimpedance analysis can be seen as a standardised test of cellular mass and function since reactance is believed to reflect the mass and integrity of cell membranes. This study investigated the association between resistance and reac- tance normalised for height (R/H and Xc/H), and muscle function as assessed by hand grip strength. Methods: 363 patients (172 male,191 female) from Berlin and Copenhagen were included in the analysis. Whole body impedance was determined by BIA 2000M (Berlin) or EFG2.0 (Copenhagen). Hand grip strength was measured with Digimax electronic hand dynamometer (Berlin) or Jamar dynamometer (Copenhagen). The general linear model was used to assess the association between R/H, Xc/H and hand grip strength. Results: We observed a significant association between the impedance parameters R/H and Xc/H and hand grip strength after adjusting for confounding variables (hand grip strength ¼36.90.063  R/ H þ 0.573  Xc/H þ 40.7  Height þ 0.115  Weight  0.09  Age þ 3.41 (gender ¼ male) þ 1.87 (Centre Berlin); Weight: P ¼ 0.04, all other coefficients: P < 0.0005. r 2 ¼ 0.708). Conclusions: The impedance parameters R/H and Xc/H are related to hand grip strength and might therefore be used as a cooperation-independent method to reproducibly assess muscle function. Ó 2008 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved. 1. Introduction Loss of function and muscle strength occurs with both disease and malnutrition and is of major clinical significance. 1 Patients who have lost more than 20% of their body weight inevitably suffer from physiological impairment. 2 Muscle function, as assessed by hand grip strength, has been reported to be closely related to total body protein and even more to protein loss. 2 However, muscle function is also frequently reduced in disease before any weight loss can be determined. Hand grip strength, a commonly used method to assess muscle function, has been shown to be predictive of postoperative complications 3,4 and predicts surgical risk better than weight loss alone. 5 It is, moreover, a superior prognostic parameter compared to biochemical and anthropometric markers of nutritional status. 6 Hand grip strength on admission to hospital has also been reported to be a predictor of loss of functional status in hospitalised patients, 7 of one year outcome in patients with liver cirrhosis, 8 and of onset of ADL (activities of daily living) dependence in the elderly. 9 Reduced midlife grip strength has also been associated with long-term mortality, 10 which suggests that higher strength might provide a greater physiologic and functional reserve that protects against mortality and morbidity. However, although hand grip strength measurement is an easy method to estimate muscle function, it still requires the patient’s cooperation in terms of compliance and ability. Alternative methods that reflect functionality would therefore be helpful in the clinical setting. Bioimpedance analysis is an easy-to-use, portable, inexpensive and non-invasive method, which has gained a lot of popularity in the last decades. It is independent of patient cooperation and can be repeated frequently. It measures whole body impedance, which is the opposition to an alternating current consisting of two compo- nents: resistance (R) and reactance (Xc). Resistance is the decrease in voltage reflecting conductivity through ionic solutions. Reac- tance is the delay in the flow of current measured as a phase-shift, reflecting dielectric properties, i.e., capacitance, of cell membranes and tissue interfaces. 11 In the Bioelectrical Impedance Vector Analysis (BIVA) approach, introduced by Piccoli et al., resistance and reactance normalised for * Correspondence to: Medizinische Klinik und Poliklinik mit SP Gastro- enterologie, Hepatologie und Endokrinologie, Charite ´ -Universita ¨ tsmedizin Berlin, 10098 Berlin, Germany. Tel.: þ49 30 450 514062; fax: þ49 30 450 514901. E-mail address: matthias.pirlich@charite.de (M. Pirlich). Contents lists available at ScienceDirect Clinical Nutrition journal homepage: http://intl.elsevierhealth.com/journals/clnu 0261-5614/$ – see front matter Ó 2008 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved. doi:10.1016/j.clnu.2008.11.001 Clinical Nutrition 28 (2009) 78–82