The Accuracy of Foot-to-Foot Bioelectrical Impedance Analysis Percentage in Adults with Down Syndrome Christopher T. Jenkins, B.S.1, Brett S. Nickerson, Ed.S.2; Angela R. Russel, M.S.1; Sara C. Bicard, Ph.D. 1; A.J. Mahurin, M.D. 1; Henry N. Williford, Ed.D. FACSM1; Michael R. Esco, Ph.D., FACSM1. 1Auburn University at Montgomery, Montgomery, AL. 2University of Alabama, Tuscaloosa, AL. Discussion Abstract Purpose Results In response to diminishing physical activity levels, individuals with Down syndrome (DS) are displaying increased levels of body fat leading to possible chronic disease and reduced quality of life. Numerous prediction methods including the foot-to-foot bioelectrical impedance analysis (FF-BIA) have been created to develop practical means of estimating BF% in the general public. Limited research is available to determine whether FF-BIA is an accurate prediction method of BF% in individuals with DS. PURPOSE: The purpose of this research was to cross-validate the FF-BIA for predicting BF% in adults with DS. METHODS: 19 adults (10 males and 9 females) with DS (age = 28.9 +/- 10.3 yrs, height = 148.6 +/- 8.7 cm, weight = 74.0 +/- 13.1 kg) volunteered to participate in this investigation. Dual energy x-ray absorptiometry (DXA) served as the measure for criterion BF%. Predicted BF% was determined with FF-BIA (Tanita TBF-521). Cross-validation statistics included T-tests, correlation procedures, and the method of Bland-Altman. RESULTS: Mean BF% was 42.5 ± 9.0% for DXA and 36.1 ± 8.5% for FF-BIA (p<0.001). The FF-BIA was highly correlated with the DXA (r=0.76, p<0.001) and had a standard error of estimate (SEE) ± 6.0%. However, the constant error (CE) for FF-BIA was -6.4% and revealed a 95% limits of agreement from -18.3% to 5.5% compared to DXA. CONCLUSIONS: This investigation demonstrated significant differences and wide limits of agreement when comparing FF-BIA and DXA and FF-BIA in a sample of adults with DS. Practitioners need to consider the results of this study before using FF- BIA among individuals with DS. The purpose of this research was to cross-validate the FF-BIA for predicting BF% in adults with DS. Mean BF% was 42.5 ± 9.0% for DXA and 36.1 ± 8.5% for FF-BIA (p<0.001). FF-BIA was highly correlated with the DXA (r = 0.76, p<0.001, Figure 1) and had a standard error of estimate (SEE) ± 6.0%. However, the constant error (CE) for FF-BIA was -6.4% and revealed a 95% limits of agreement from -18.3% to 5.5% compared to DXA (Figure 2). As increased overweight and obesity trends have become prevalent in the DS community, a reliable means of determining BF% in these individuals is essential in combating and potentially reversing these current unhealthy trends. The FF-BIA has become a popular screening technique due to its practicality and non-invasive means of testing BF%. Previous research has provided contradictory results in the validity of BIA predicting individualized and mean BF% in various populations (2,4,5). The present study attempted to decipher whether this form of FF measurement would prove bias towards the unique physical characteristics common to individuals with DS and determine whether it is a valid means of predicting BF% in this population. The results of this investigation demonstrated significant differences and wide limits of agreement when comparing FF-BIA and DXA and FF-BIA in a sample of adults with DS. Due to the variances displayed, FF-BIA may not be appropriate to predict BF% in this population and practitioners need to consider the results of this study before using FF-BIA among individuals with DS. Methods Subjects 19 adults (10 males and 9 females) with DS (age = 28.9 +/- 10.3 yrs, height = 148.6 +/- 8.7 cm, weight = 74.0 +/- 13.1 kg) volunteered to participate in this investigation. This study was approved by the Institutional Review Board for Human Participants, and written informed consent was obtained from each subject. Body Fat Percentage Assessment Predicted BF% was determined with FF-BIA (Tanita TBF-521). References Figure 1. Scatter plot representing the relationship between DXA and BIA American College of Sports Medicine. ACSM’s Guidelines for Exercise Testing and Prescription, 8th Edition. Philadelphia, PA: Wolters Kluwer, 2010. Dehghan, M. and Merchant, AT. Is bioelectrical impedance accurate for use in large epidemiological studies? Nutrition Journal. 2008; 7(26). Hill, DL., Parks, EP., Zemel, BS., Shults, J., Stallings, VA., and Stettler, N. Resting energy expenditure and adiposity accretion among children with down syncrome: a three year prospective study. European Journal of Clinical Nutrition. 2013; 67(10): 1087-1091. Macfarlane, D. Can bioelectric impedance monitors be used to accurately estimate body fat in chinese adults? Asia Pacific Journal of Clinical Nutrition. 2007; 16(1): 66-73. Radley, D., Cooke, CB., Fuller, NJ., Oldroyd, B., Truscott, JG., Coward, WA., Wright, A., and Gately, PJ. Validity of foot-to-foot bio-electrical impedance analysis body composition estimates in overweight and obese children. International Journal of Body Composition Research. 2010; 7(1): 15-20. Seron, BB., Silva, RA., and Greguol, M. Effects of two programs of exercise on body composition of adolescents with down syndrome. Rev Paul Pediatrics. 2014; 32(1): 92-8. Introduction Dual energy x-ray absorptiometry (DXA) served as the measure for criterion BF%. Increased BF% is a common physical characteristic that is shared amongst individuals with DS (6). While this population is now experiencing greater life durations (6), a greater emphasis has been placed on increasing overall quality of life through the prevention of obesity related diseases. As an increase in adipose tissue has been shown to be a major contributing factor for various chronic diseases (1), a practical means of BF assessment that adheres to characteristics unique to this population is pivotal in providing appropriate health screenings and prescriptions for individuals with DS. The FF-BIA is a convenient and popular means of measuring BF% through the use of an electrical stimulus that travels through the lower regions of the body and provides estimations based on the speed and resistance of the current (2). While DS produces unique physical characteristics, it has been questioned whether this practice of assessment is appropriate for this population. Data Analysis Cross-validation statistics included T-tests, correlation procedures, and the method of Bland-Altman. Figure 2. Bland- Altman Plot representing the limits of agreement between the DXA and BIA This presentation was funded by the Research Council and Office of the Associate Provost for Research and Graduate Studies at Auburn University Montgomery