The relation between skeletal maturation and adiposity in African American and Caucasian children.
OBJECTIVE
African American children have earlier pubertal and skeletal maturation and a higher body mass index (BMI) than Caucasian children. We tested the hypothesis that advanced bone age in African American children is accounted for by their greater adiposity.


METHODS
We studied 252 African American (n = 97) and Caucasian (n = 155) children aged 5 to 12 years. Skeletal age was determined by a radiologist blinded to clinical details. The difference between bone age (BA) and chronological age (CA) (noted as BA - CA) and the ratio of bone age to chronological age (BA/CA) were determined. Analysis of covariance was used to adjust skeletal maturation for the effects of adiposity, as measured by BMI, BMI standard deviation score (BMI SDS), and fat mass by dual energy x-ray absorptiometry (DXA).


RESULTS
African American children were significantly heavier than Caucasians (BMI SDS 2.7 +/- 3.4 vs 1.7 +/- 2.4, P <.05). Both BA - CA (0.75 +/- 1.46 vs 0.28 +/- 1.38, P <.05) and BA/CA (1.09 +/- 0.17 vs 1.03 +/- 0.16, P <.05) were significantly greater in African Americans than Caucasians. BA - CA and BA/CA were significantly correlated with lean body mass, BMI, BMI SDS, and DXA fat mass (all r > 0.46, P <.001). Neither BA - CA nor BA/CA of African Americans and Caucasians were significantly different after correction for lean body mass and measures of adiposity, including BMI, BMI SDS, or DXA fat mass.


CONCLUSIONS
Skeletal age is more advanced in African American than Caucasian children and is significantly related to body mass. In large measure, the advancement in skeletal maturation of prepubertal and early pubertal African American children can be accounted for by their greater adiposity.
Russell
D L
DL
Unit on Growth and Obesity, Developmental Endocrinology Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA.
Keil
M F
MF
Bonat
S H
SH
Uwaifo
G I
GI
Nicholson
J C
JC
McDuffie
J R
JR
Hill
S C
SC
Yanovski
J A
JA
D015502:Absorptiometry, Photon; D000273:Adipose Tissue / Q000000981:diagnostic imaging / Q000254:growth & development*; D000365:Age Determination by Skeleton; D000704:Analysis of Variance; D044383:Black People / Q000235:genetics*; D001827:Body Height / Q000235:genetics; D015992:Body Mass Index; D001835:Body Weight / Q000235:genetics; D001846:Bone Development / Q000235:genetics*; D002648:Child; D002657:Child Development; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008297:Male; D009765:Obesity / Q000000981:diagnostic imaging / Q000235:genetics; D011627:Puberty / Q000235:genetics; D044465:White People / Q000235:genetics*; D001741:Black or African American