Subject Characteristics
The subject demographic and body composition data are presented in Table . The multiethnic group included 147 children (ages 5 – 17 years; n = 88 males and 59 females) and 352 adults (age ≥ 18 years; n = 164 males and 188 females). The adult and child groups had mean BMIs or BMI percentiles approximating those observed in the general US population [
19,
20]. Among the adults, males were younger than females (P < 0.001) and there were no sex differences in BMI. Age and BMI percentiles in the child group did not differ significantly between males and females.
Adipose Tissue Components
Total adipose tissue was significantly smaller in the adult males than in the females (18.8 ± 8.1 L vs. 25.2 ± 11.9 L; p < 0.001). TAT was also significantly smaller in the boys than in the girls (13.4 ± 9.5 L vs. 17.7 ± 12.5 L; p = 0.020).
VAT was significantly greater in the adult males than in the females (2.1 ± 1.8 L vs. 1.4 ± 1.2 L; p < 0.001). There were no sex differences in VAT in the children (0.6 ± 0.5 vs. 0.6 ± 0.5 L; p = 0.762).
SAT volume was significantly smaller in the adult males than in the females (16.5 ± 6.9 L vs. 23.7 ± 11.1 L; p < 0.001) and significantly smaller in the boys than in the girls (12.2 ± 8.5 vs. 16.4 ± 11.6 L; p = 0.013).
Age and Sex Effects
The regression equations for each adipose tissue component are presented in Table . The smoother line for VAT and SAT volumes versus age are shown in Figure and Figure , respectively. The figure shows that VAT and SAT are both larger with greater age across the entire age range except for a reverse trend before age 17 years in females (i.e., VAT at age 7, 0.70 L, VAT age 17, 0.48 L). Males had a larger amount of VAT than females after age 12 years and this difference remained throughout the remaining age range (Figure ). In contrast, females had a larger SAT volume than males across the whole age range (Figure ). In both males and females, the slope of the regression line between SAT and age was smaller for subjects over the age of 50 years older than for their younger counterparts (slopes in males, 0.003 vs 0.204; slopes in females, 0.021 vs 0.322).
| Table 2Regression equations for adipose tissue compartments (n = 499). |
After adjustment for TAT volume and ethnicity, in males VAT was smaller with greater age before the age of 12 years and VAT was larger after the age of 12 years throughout the remaining age range (Figure ). After adjustment for TAT, ethnicity, and menopause status in females, VAT was smaller with greater age before the age of 26 years and larger after the age of 26 years throughout the remaining age range (Figure ). After adjustment for TAT volume and ethnicity, SAT was larger for older age before the age of 17 years in males and smaller after the age of 17 years throughout the remaining age range (Figure ). In females SAT was larger with increasing age before the age of 35 years and SAT was smaller with increasing age after the age of 35 years (Figure ).
Menopause Effects
When regression analyses for both VAT and SAT were completed in pre- and post- menopausal women separately, age2 (P = 0.003, P < 0.001 for VAT and SAT respectively) and age3 (P = 0.001, P < 0.001 for VAT and SAT respectively) significantly entered the model in pre-menopausal women. However, there were non-significant relationships between age and SAT (P = 0.130) and age and VAT (P = 0.872) in postmenopausal women. When pre- and post- menopausal women were pooled, menopausal status was no longer significant for both VAT and SAT, either as an individual term (VAT, P = 0.279; SAT, P = 0.272) or as interactions with age (VAT, P = 0.284; SAT, P = 0.440).
The increase of VAT was calculated for every age decade. In women, the VAT increases from ages 40 to 50 years (i.e., mean volume, 0.55 L) and from age 50 to 60 years (i.e., mean volume, 0.45 L) were the largest observed.
Puberty Effects
There were a total of 115 children (i.e., ~78%) with pubertal status available. One 16 year old child with Tanner Stage 1 was excluded from the data analysis as an outlier. When regression analyses for both VAT and SAT were completed in pre-pubertal and pubertal children separately, age did not significantly (P = 0.495, P = 0.337 for VAT and SAT, respectively) enter the model in pre-pubertal children when controlled for sex (Table ). On the other hand, age borderline significantly or significantly (P = 0.068, P = 0.004 for VAT and SAT, respectively) entered the model in pubertal children when controlled for sex (Table ). Sex did not significantly enter the models in prepubertal children for VAT (P = 0.235), and SAT (P = 0.259). In pubertal children, sex was significant in the SAT model (P = 0.004) but not in the VAT model (P = 0.722). When pre-pubertal and pubertal children were pooled, age significantly entered the model for VAT (P = 0.021) and SAT (P = 0.001). In the pooled data, pubertal status was not significant for both VAT and SAT, either as an individual term (VAT, P = 0.907; SAT, P = 0.718) or as interactions with age (VAT, P = 0.802; SAT, P = 0.415).
| Table 3Regression equations for adipose tissue compartments in prepubertal and pubertal children. |