Characteristics of participants
A total of 935 school-age children (546 boys and 389 girls) were included in this analysis, aged 7 to 12 years. The detailed characteristics of the normal weight and overweight/obesity participants are presented in Table 1. Compared with normal weight subjects, children with overweight and obesity were older, mostly urban children; had higher BMI, heart rate, SBP, DBP, PP and MAP; higher body fat, muscle mass, protein mass, FAT%, visceral fat area and visceral fat level (P < 0.05). Compared with boys, girls with overweight and obesity had a higher heart rate, body fat and FAT%; lower SBP, PP, muscle mass, protein mass, visceral fat area and visceral fat level (P < 0.05).
Table 1
Blood Pressure-Related Indexes and Body Composition Characteristics of School-Age Children (n = 935)
Variables | Normal weight (n = 307) | Overweight/obesity (n = 628) | P value | Overweight/obesity | P value |
Boys (n = 378) | Girls (n = 250) |
Setting | | | 0.002 | | | 0.229 |
Urban | 140 (45.60) | 356 (56.69) | | 221 (58.47) | 134 (53.60) | |
Rural | 167 (54.40) | 273 (43.31) | | 157 (41.53) | 116 (46.40) | |
Age (years) | 9.17 (8.53–10.85) | 10.00 (8.90-11.21) | < 0.0001 | 10.13 (8.82–11.35) | 9.79 (8.95–11.01) | 0.124 |
Height (cm) | 138.51 ± 9.95 | 144.97 ± 9.38 | < 0.0001 | 145.22 ± 9.28 | 144.60 ± 9.54 | 0.420 |
BMI (kg/m2) | 17.40 (16.30–18.60) | 23.00 (20.90–25.40) | < 0.0001 | 23.40 (21.18–25.60) | 22.40 (20.70–25.10) | 0.057 |
Heart rate (bpm) | 95 ± 13 | 100 ± 14 | < 0.0001 | 99 ± 14 | 102 ± 13 | 0.003 |
SBP (mm Hg) | 94.33 (89.00-101.67) | 104.67 (97.67–112.50) | < 0.0001 | 106.38 ± 10.82 | 103.91 ± 12.1 | 0.008 |
DBP (mm Hg) | 63.67 (59.00-69.33) | 69.00 (62.67–75.67) | < 0.0001 | 70.11 ± 9.24 | 69.72 ± 9.66 | 0.606 |
PP (mm Hg) | 31.33 (26.00-35.33) | 34.67 (29.33–41.17) | < 0.0001 | 36.26 ± 8.62 | 34.19 ± 9.27 | 0.004 |
MAP (mm Hg) | 74.70 ± 7.80 | 81.77 ± 9.21 | < 0.0001 | 82.20 ± 8.91 | 81.12 ± 9.62 | 0.147 |
Body fat (kg) | 4.40 (2.85–5.90) | 11.60 (8.10–15.40) | < 0.0001 | 11.00 (7.10-14.43) | 12.70 (2.30–3.20) | < 0.0001 |
Muscle mass (kg) | 27.36 ± 5.76 | 34.55 ± 6.40 | < 0.0001 | 35.96 ± 6.17 | 32.41 ± 6.15 | < 0.0001 |
Protein (kg) | 6.27 ± 1.42 | 7.60 ± 1.34 | < 0.0001 | 7.98 ± 1.24 | 7.03 ± 1.27 | < 0.0001 |
FAT (%) | 13.40 ± 5.84 | 23.87 ± 5.94 | < 0.0001 | 21.90 (17.15–25.90) | 26.80 (24.00-30.80) | < 0.0001 |
Visceral fat area (cm2) | 25.00 (23.00–30.00) | 58.00 (38.75-72.00) | < 0.0001 | 69.00 (55.00–80.00) | 37.00 (29.00-54.75) | < 0.0001 |
Visceral fat level# | | | < 0.0001 | | | < 0.0001 |
Subcutaneous/balanced | 293 (100.00) | 477 (76.81) | | 267 (71.39) | 210 (85.02) | |
Critical visceral obesity | 0 | 90 (14.49) | | 62 (16.58) | 28 (11.34) | |
Visceral obesity | 0 | 54 (8.70) | | 45 (12.03) | 9 (3.64) | |
Data are median (interquartile range) or no. (%). |
# Partial data deletion. |
BMI, body mass index; SBP, systolic blood pressure; DBP, diastolic blood pressure; PP, pulse pressure; MAP, mean arterial pressure; FAT%, body fat percentage. |
The distribution of EBP, EPP and EMAP in children with overweight and obesity
Compared with normal BMI children, participants with overweight/obesity had higher EBP, EPP and EMAP proportions (P < 0.05), especially for boys. In addition, as BMI increased in boys the proportion of normal BP, PP and MAP decreased, and the proportion of EBP, EPP and EMAP increased. Among girls, only BP and MAP indicated the same trend (Table S1). In particular, with an increase of BMI, BP showed a linear increasing trend in both boys and girls (P < 0.05). Similarly, compared with children of normal FAT% and visceral fat levels, participants with overweight and obesity had higher EBP, EPP and EMAP proportions (Table S2 and Table S3). Moreover, FAT% and visceral fat levels seem to be more sensitive than BMI; with an increase of FAT% and visceral fat levels, the proportion of EPP in girls with overweight and obesity also showed an increasing trend compared with girls of normal weight.
Adjusted population attributable risk of overweight/obesity for EBP, EPP and EMAP
The associations of overweight and obesity with EBP, EPP and EMAP were evaluated by multivariate logistic regression analysis. Compared with normal weight, overweight and obesity were associated with EBP, EPP and EMAP after adjusting for age, sex, setting, height and heart rate. Especially in boys, as BMI increased this association gradually increased. However, overweight and obesity were only associated with EBP and EMAP of school-age girls after adjusting for age, setting, height and heart rate. Because the EPP group of girls was not accompanied by visceral obesity, logistic regression analysis did not show results (Table S4).
The PAR of EBP and EMAP attributable to overweight and obesity was greater than that of EPP. Moreover, for boys, overweight and obesity accounted for more PAR for EBP, EPP and EMAP. EBP in about 78% of children overall (79% of boys and 76% of girls) could be attributed to visceral fat level, and EBP in about 71% of children overall (76% of boys and 65% of girls) could be attributed to BMI. Visceral fat level accounted for PAR of EBP more so than BMI. However, BMI was superior to FAT% and visceral fat level in estimating the PAR of EPP and EMAP (Table 2).
Table 2
Adjusted Population Attributable Risk of Overweight/obesity for Elevated BP, PP and MAP
| No. of pre-EBP/EBP | No. of overweight | No. of obesity | PAR% | No. of EPP | No. of overweight | No. of obesity | PAR% | No. of EMAP | No. of overweight | No. of obesity | PAR% |
Overall | | | | | | | | | | | | |
BMI | 329 | 72 | 198 | 71 | 96 | 24 | 60 | 64 | 93 | 18 | 68 | 80 |
FAT% | 68 | 49 | 64 |
Visceral fat level | 78 | 18 | 72 |
Boys | | | | | | | | | | | | |
BMI | 194 | 41 | 126 | 76 | 66 | 17 | 42 | 66 | 53 | 9 | 41 | 82 |
FAT% | 76 | 57 | 74 |
Visceral fat level | 79 | 30 | 72 |
Girls | | | | | | | | | | | | |
BMI | 135 | 31 | 72 | 65 | 30 | 7 | 18 | 61 | 40 | 9 | 27 | 78 |
FAT% | 57 | 38 | 45 |
Visceral fat level | 76 | — | 57 |
EBP, elevated blood pressure; EPP, elevated pulse pressure; EMAP, elevated mean arterial pressure; PAR, population-attributable risk. |
Correlation of overweight and obesity with BP, PP and MAP
The BMI, FAT% and visceral fat area of school-age children strongly correlated with SBP and MAP, especially for boys, and the correlation coefficients r > 0.5. Moreover, BMI and visceral fat area were consistent, and both showed strong correlation with BP, PP and MAP (Table S5).
The effects of obesity on SBP, DBP, PP and MAP with different height and age
SBP, PP and MAP of school-age children increased with height, regardless of gender. But changes in DBP with height were more complicated. The relationship between blood pressure and height was augmented comparably in children with overweight and obesity (based on BMI) (Fig. 1). SBP, DBP, PP and MAP were higher with age in boys, especially for boys with overweight and obesity. But only SBP and PP increased with age, while DBP and MAP showed complex trends among girls. Similarly, the interaction between blood pressure and age in children with overweight and obesity was also increased (Fig. 2).