Fat and lean masses in youths with Down syndrome: Gender differences
Highlights
► Youths with Down syndrome have different fat and lean distributions than controls. ► Their sexual dimorphism looks similar than the observed in controls. ► Youths with DS could be at higher risk of metabolic syndrome.
Introduction
Increased adiposity characterized by a higher percentage of body fat (%BF) during childhood and adolescence is related to a greater risk of premature illnesses, death from coronary heart disease, hypertension and type 2 diabetes mellitus later in life (Dietz, 1998, Ebbeling et al., 2002, Maffeis and Tato, 2001). Low lean mass is associated with decreased skeletal muscle tissue (Calbet et al., 2008), which that in turn, reduces the functional capacity and the maximum oxygen consumption that is a marker of health in youth and is also associated with increased cardiovascular health later in life (Ortega et al., 2005, Ortega et al., 2008). Although certain clinical studies indicate that a common characteristic of youths with Down syndrome (DS) is to have light to moderate obesity (Chumlea and Cronk, 1981, Cronk et al., 1985, Hawn et al., 2009, Rubin et al., 1998), and that no difference in fat-free mass can be found when compared with youths without DS (Luke, Sutton, Schoeller, & Roizen, 1996), soft-tissue body composition in children and adolescents with DS has not been sufficiently studied (González-Agüero et al., 2010).
Although cardiovascular disease is not one of the most common disorder related to mortality in this population (Coppus et al., 2008, Prasher, 1993, Thase, 1982) and despite the fact that persons with DS may have fewer atherosclerotic risk factors than others with intellectual disability without DS (Draheim, McCubbin, & Williams, 2002), the continuous increase in life expectancy in the DS population (from 9 to 55 years and older during the last 70 years) (Bittles and Glasson, 2004, Glasson et al., 2002, Smith, 2001) together with high levels of adipose tissue (especially in the trunk) (Dietz, 1998, Ebbeling et al., 2002, Maffeis and Tato, 2001, Ortega et al., 2005, Ortega et al., 2008) might be a future health issue.
In this regard, Bronks and Parker (1985) described that although the %BF assessed with anthropometry in participants with DS did not significantly change with age, it was consistently high at all ages, suggesting that fat mass accumulation occurs prior to adulthood.
In adults, studies assessing the %BF by dual energy X-ray absorptiometry (DXA) showed higher levels of fat mass and lower levels of lean mass in participants with DS compared with age- and sex-matched controls without DS (Baptista et al., 2005, Guijarro et al., 2008).
Air-displacement plethysmography (ADP) has been used to assess body composition in children and adolescents because of its accuracy and validity of estimation at the individual level (Fields and Goran, 2000, Parker et al., 2003). However, to our knowledge only one study assessed DS adults with ADP (Usera, Foley, & Yun, 2005). In addition, DXA offers the possibility of performing regional analyses (trunk, upper and lower limbs) of fat and lean masses.
On the other hand, due to the high cost and large dimensions of those two methods, a limited number of studies have been performed on DS populations (Angelopoulou et al., 1999, Baptista et al., 2005, Guijarro et al., 2008).
The difficult conditions of these two methods make them unsuitable for field and clinical use; therefore other methods such as anthropometry are also widely used. Waist circumference (WC) seems to be one of the best anthropometric indicator for increased risk of metabolic syndrome in healthy children (Moreno et al., 2002); however no data on populations with DS can be found on this regard. It is important to note that we used a combination of three methods (DXA, ADP and WC) in order to better evaluate the body composition of this population, and to assess the effectiveness of WC as a predictor of high adiposity levels in a population with DS.
Lastly, due to the lack of information related to body composition in youths with DS, it is still unknown whether the common sexual dimorphism presents in youths without DS is also present in children and adolescents with DS.
Thus the aims of the present study were: (1) to compare total and regional distributions of fat and lean masses between male and female children and adolescents with and without DS; (2) to investigate whether WC can accurately detect those individuals with an elevated level of adiposity; and (3) to evaluate the presence of sexual dimorphism in children and adolescents with DS.
Section snippets
Participants
A total sample of 31 children and adolescents with DS (14 females/17 males, aged 10–19 years) were recruited from different schools and institutions of Aragón (Spain). An age- and sex-matched control group composed of 32 participants (13 females/19 males) without DS was recruited from a public school also in Aragón. All participants without DS were healthy, without known illness and free of medication for at least 3 months before the beginning of the study.
Full clinical histories, including
Physical characteristics
Age and physical characteristics of the participants are summarized in Table 1. In general, participants with DS were lighter and smaller than those without DS (all p ≤ 0.05). No differences in age, BMI and WC were observed between groups or between genders within the same group.
Percentage of body fat
The %BF assessed by ADP and DXA is presented in Table 2. Females in both groups (with and without DS) had a higher %BF than the males from their respective groups (all p ≤ 0.05). No differences between groups were observed
Discussion
Although some previous studies have evaluated body composition in adults with DS using either DXA or ADP (Baptista et al., 2005, Usera et al., 2005), to our knowledge, this is the first study that includes body composition assessment in children and adolescents with DS using DXA, ADP and WC at the same time. The main finding of the present study is that, despite similar values of WC, BMI and %BF (both with DXA and ADP) between populations with and without DS, different distributions of fat and
Conclusions
The current investigation provides evidence that children and adolescents with DS have higher levels of total and regional fat mass than their counterparts without DS. Furthermore, BMI, WC and %BF seem not to be accurate enough to detect an excess of adiposity in this population. As a consequence, more precise studies of the body composition in this specific population are required, with particular attention being paid in evaluating regional adiposity levels and the implications for future
Acknowledgments
The authors want to thank all the children and their parents that participated in the study for their understanding and dedication to the project. Special thanks are given to Fundación Down Zaragoza and Special Olympics Aragon for their support. We also thank Scott G Mitchell from the University of Glasgow and Steven J James for his work of reviewing the English style and grammar, and Paula Velasco from the University of Zaragoza for her great technical assistance. This work was supported by
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