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Bioelectrical impedance analysis and age-related differences in body composition in the elderly
Nutrition, Metabolism & Cardiovascular Diseases (2008) 18, e31
available at www.sciencedirect.com
journal homepage: www.elsevier.com/locate/nmcd
LETTER TO THE EDITOR
Bioelectrical impedance analysis and age-related differences in body composition in the elderly We thank Buffa et al. for their letter, offering us the opportunity to clarify some aspects regarding our most recent publication in Nutrition, Metabolism & Cardiovascular Diseases (2007; 17:175e80). Firstly, we agree with Buffa et al. on the importance of adjusting bioelectrical parameters for body size [1]. However, we advise this method only for studies comparing groups with significant differences in body weight. In our study, age groups had a similar body weight and body mass index within each BMI class, probably because of the small sample size. However, the homogeneity of our sample strengthens the results we obtained in each BMI class, when comparing different age groups. Secondly, the effects of ageing on phase angle are evident in the oldest (70e80 years) of all groups (normal, overweight and obese). This age-related difference, however, was significant in our study only in the overweight and obese oldest (70e80 years). This trend has also been found in other larger studies on healthy adults [2,3]. Figure 2 was intended to clarify this phenomenon in the oldest subjects (70e80 years), because the mean vector displacement with a downward migration of the ellipses was significant in overweight and obese subjects (group labels b and c, respectively, referred to the ellipses) and were reported at the bottom of the figure. The specifications a, b and c that appeared in figure 2 on the top of the y axis identify only each graph in the figure. We apologize for the labelinduced misunderstanding, if this was the case. Third, all evidence indicates that age-related changes in the phase angle are complex and they are determined by
age-related body composition modification, BMI and their interaction. In our study we suggested that the accelerating factor of normal age-related decline in phase angle and/or skeletal muscle mass, is the overweight and/or obesity status. On the other hand, it is important to note that in their study Buffa et al. did not stratify the Sardinian (Italian) population according to BMI categories so that each age class included all the BMI groups observed. It would be interesting to know the prevalence of overweight and obesity in the Sardinian population. Therefore, a prevalence of normal weight on overweight and obese subjects might have led to a late decrease in phase angle with ageing.
References [1] Buffa R, Floris G, Marini E. Migration of the bioelectrical impedance vector in healthy elderly subjects. Nutrition 2003;19:917e21. [2] Kyle UG, Genton L, Slosman DO, Pichard C. Fat-free and fat mass percentiles in 5225 healthy subjects aged 15 to 98 years. Nutrition 2001;17:534e41. [3] Wu TJ. Relationships between age, sex, anthropometry and bioelectrical impedance. J Formos Med Assoc 1992;91: 1143e7.
DOI of original article: 10.1016/j.numecd.2008.01.011. 0939-4753/$ - see front matter ª 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.numecd.2008.02.010
Bruna Guida Federico II University, Physiology Nutrition Section, Department of Neuroscience, Via S. Pansini 5, 80131 Napoli, Italy E-mail address: [email protected]
17 January 2008
available at www.sciencedirect.com
journal homepage: www.elsevier.com/locate/nmcd
LETTER TO THE EDITOR
Bioelectrical impedance analysis and age-related differences in body composition in the elderly We thank Buffa et al. for their letter, offering us the opportunity to clarify some aspects regarding our most recent publication in Nutrition, Metabolism & Cardiovascular Diseases (2007; 17:175e80). Firstly, we agree with Buffa et al. on the importance of adjusting bioelectrical parameters for body size [1]. However, we advise this method only for studies comparing groups with significant differences in body weight. In our study, age groups had a similar body weight and body mass index within each BMI class, probably because of the small sample size. However, the homogeneity of our sample strengthens the results we obtained in each BMI class, when comparing different age groups. Secondly, the effects of ageing on phase angle are evident in the oldest (70e80 years) of all groups (normal, overweight and obese). This age-related difference, however, was significant in our study only in the overweight and obese oldest (70e80 years). This trend has also been found in other larger studies on healthy adults [2,3]. Figure 2 was intended to clarify this phenomenon in the oldest subjects (70e80 years), because the mean vector displacement with a downward migration of the ellipses was significant in overweight and obese subjects (group labels b and c, respectively, referred to the ellipses) and were reported at the bottom of the figure. The specifications a, b and c that appeared in figure 2 on the top of the y axis identify only each graph in the figure. We apologize for the labelinduced misunderstanding, if this was the case. Third, all evidence indicates that age-related changes in the phase angle are complex and they are determined by
age-related body composition modification, BMI and their interaction. In our study we suggested that the accelerating factor of normal age-related decline in phase angle and/or skeletal muscle mass, is the overweight and/or obesity status. On the other hand, it is important to note that in their study Buffa et al. did not stratify the Sardinian (Italian) population according to BMI categories so that each age class included all the BMI groups observed. It would be interesting to know the prevalence of overweight and obesity in the Sardinian population. Therefore, a prevalence of normal weight on overweight and obese subjects might have led to a late decrease in phase angle with ageing.
References [1] Buffa R, Floris G, Marini E. Migration of the bioelectrical impedance vector in healthy elderly subjects. Nutrition 2003;19:917e21. [2] Kyle UG, Genton L, Slosman DO, Pichard C. Fat-free and fat mass percentiles in 5225 healthy subjects aged 15 to 98 years. Nutrition 2001;17:534e41. [3] Wu TJ. Relationships between age, sex, anthropometry and bioelectrical impedance. J Formos Med Assoc 1992;91: 1143e7.
DOI of original article: 10.1016/j.numecd.2008.01.011. 0939-4753/$ - see front matter ª 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.numecd.2008.02.010
Bruna Guida Federico II University, Physiology Nutrition Section, Department of Neuroscience, Via S. Pansini 5, 80131 Napoli, Italy E-mail address: [email protected]
17 January 2008