DEVELOPMENTAL MEDICINE & CHILD NEUROLOGY
ORIGINAL ARTICLE
Assessment of body composition in children with cerebral palsy: a cross-sectional study in Norway ANE-KRISTINE FINBR ATEN 1,2 | CATIA MARTINS 3 | GURO LILLEMOEN ANDERSEN 1,4 | JON SKRANES 1 | IUSSON 5,7 | UNNI SYVERSEN 3,8 | RICHARD D STEVENSON 9 BENTE BRANNSETHER 5,6 | P ETUR BENEDIKT J UL TORSTEIN VIK
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1 Department of Laboratory Medicine, Children’s and Women’s Health, Norwegian University of Science and Technology, Trondheim; 2 Department of Pediatrics, St. Olav’s University Hospital, Trondheim; 3 Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, Trondheim; 4 The Cerebral Palsy Register of Norway, Habilitation Center, Vestfold Hospital Trust, Tønsberg; 5 Department of Clinical Science, University of Bergen, Bergen; 6 Department of Pediatrics, Stavanger University Hospital, Stavanger; 7 Department of Pediatrics, Haukeland University Hospital, Bergen; 8 Department of Endocrinology, St. Olav’s University Hospital, Trondheim, Norway. 9 Department of Pediatrics, Division of Developmental Pediatrics, Kluge Children’s Rehabilitation Center and Research Institute, University of Virginia, Charlottesville, VA, USA. Correspondence to Ane-Kristine Finbr aten at Olav Kyrres gt.11, N-7489 Trondheim, Norway. E-mail:
[email protected] This article is commented on by Sullivan on pages 793–794 of this issue.
PUBLICATION DATA
Accepted for publication 9th February 2015. Published online 1st April 2015. ABBREVIATIONS
BMI DXA SFT
Body mass index Dual-energy X-ray absorptiometry Skinfold thickness
AIM The assessment of growth and body composition is challenging in children with cerebral palsy (CP). The aim of this study was to compare clinical assessments of body composition with measurements obtained using dual-energy X-ray absorptiometry (DXA) in this population. METHOD Knee height, weight, and triceps and subscapular skinfold thickness (SFT) were measured in 47 children with CP (age range 8–18y; 18 females, 29 males). Height was estimated from knee height, and used to calculate body mass index (BMI). Using SFT measurements, body fat percentage was calculated by standard (‘Slaughter’) and CPmodified (‘Gurka’) equations and compared with results obtained using DXA. RESULTS Children with severe gross motor function impairments (Gross Motor Function Classification System [GMFCS] level III or IV) exhibited stunted growth and had higher fat percentages and lower lean body mass than children classified in GMFCS level I or II. In 10 children classified as ‘thin’ according to their BMI (five of whom were assigned thinness grade of 2 or lower), percentage of body fat, as determined by DXA, was normal or high. The Slaughter equations significantly underestimated body fat percentages, whereas the precision of the CP-modified Gurka equations was excellent. INTERPRETATION In this study, children with CP and severe motor impairments displayed stunted growth, but were not undernourished. Relying solely upon BMIs may be misleading in children with CP. Therefore, clinicians should be encouraged to measure SFT and to calculate body fat percentages using the CP-modified version of the Slaughter equation.
Children with cerebral palsy (CP), in particular those with more severe motor impairments, commonly have feeding difficulties and swallowing problems resulting in malnutrition and poor growth.1 However, assessment of nutritional status is more challenging in these children than in typically developing children since a significant proportion are unable to stand upright and many have scoliosis and/or joint contractures, making height assessments difficult.2 The interpretation of weight measurements is also more challenging, since children with CP have reduced muscle and bone mass compared with typically developing children.3 The three proxies most commonly used to assess the nutritional status of typically developing children, weight-to-height ratio (body mass index [BMI]), heightfor-age, and weight-for-age, should therefore be interpreted with caution in children with CP.4 Nonetheless, 858 DOI: 10.1111/dmcn.12752
these measurements, and in particular BMI, continue to be used to assess growth, body composition, and nutritional status in this population.1,5 One of the reference methods that can be used to assess body composition is whole-body dual-energy X-ray absorptiometry (DXA). This method has been validated for use in children with CP,6 but is expensive and time-consuming. In clinical practice, body fat may be assessed by skinfold thickness (SFT) measurements, and, based upon such measurements, Slaughter et al.7 proposed equations to calculate body fat percentages in typically developing children. These equations have also been applied in studies of children with CP.8–10 However, Gurka et al.8 found that the Slaughter equations underestimated percentage body fat in children with CP, and modified these equations by correcting for several factors including gross motor © 2015 Mac Keith Press
function.8 We are aware of only two studies that have validated these ‘CP-specific’ equations, and these studies have shown conflicting results.9,11 Whereas one study found the modified equations to perform well, the other found that the equations performed poorly. The aim of the present study was to assess body composition in a Norwegian sample of children with CP, using standard clinical methods, as well as DXA. We hypothesized that the body composition of children with CP would be misjudged if based upon weight-for-age or BMI only, whereas measurements of SFT would provide better estimates.
METHOD Study population Children with CP across all functional ability levels, who lived near the city of Trondheim in the counties of Sørand Nord-Trøndelag, Norway, were invited to participate in this cross-sectional study. The goal was to include 50 children in the study, in accordance with the Consensusbased Standards for the Selection of Health Measurement Instruments checklist.12 Among the 64 children invited, 52 (80%) agreed to participate (20 females, 32 males) and were examined by one of the authors (A-KF), and from these we obtained whole-body DXA measurements for 47 (90%; 18 females, 29 males). One child was of African ethnicity; the others were white. Whole-body DXA and anthropometric measurements were obtained independently on the same day. Measurements Dual-energy X-ray absorptiometry Whole-body DXA (Discovery DXA system; Hologic, Bedford, MA, USA) was performed to assess body composition. A trained clinical technician performed the scans while participants were in a supine position. The technician was unaware of the results of the anthropometric measurements, with the exception of height (which was required to perform the DXA scan). Whole-body fat percentage was used as the primary outcome variable. Total lean mass and total bone mass were also measured, and percentages then calculated. We classified participants into three categories, based on those suggested by Lohman,13 according to their percentage body fat: low body fat (≤10% for males, ≤15% for females), adequate body fat (11–25% for males, 16–30% for females), or excess body fat (>25% for males, >30% for females). Anthropometry All anthropometric measurements were recorded twice on each side of the body by the same researcher (A-KF), and then the mean values were calculated. Weight was measured with an electronic chair scale (M40010, ADE, Hamburg, Germany) to the nearest 100g. Height was measured in a standing position in children able to stand using a fixed stadiometer to the nearest 0.1cm. Knee height was measured on both legs in all children, to the nearest
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What this paper adds Children with cerebral palsy (CP) who are classified as thin based on body mass index (BMI) calculations may have adequate or excess body fat. BMI, weight z-score, and skinfold thickness alone may be misleading in the assessment of nutritional status in children with CP. Equations based upon skinfold thickness measurements and modified for use in children with CP can reliably estimate percentage body fat.
0.1cm, with a calliper (Holtain Ltd, Crosswell, UK), and estimated heights were calculated as described by Stevenson.2 We used both standing heights and estimated heights to calculate BMIs (kg/m2). Children were further categorized into six groups based on their BMIs, in accordance with international classifications: grade 3 thinness (corresponding to an adult BMI