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BMI as a mediator of the relationship between muscular fitness and cardiometabolic risk in children: a mediation analysis.

Díez-Fernández A, Sánchez-López M, Gulías-González R, Notario-Pacheco B, Cañete García-Prieto J, Arias-Palencia N, Martínez-Vizcaíno V - PLoS ONE (2015)

Bottom Line: Muscular fitness levels have been associated with cardiometabolic risk in children, although whether body weight acts as a confounder or as an intermediate variable in this relationship remains controversial.BMI mediates the association between muscular fitness and cardiometabolic risk in schoolchildren.Overall, good muscular fitness is associated with lower cardiometabolic risk, but particularly when accompanied by normal weight.

View Article: PubMed Central - PubMed

Affiliation: Social and Health Care Research Center, University of Castilla-La Mancha, Cuenca, Spain; Faculty of Occupational Therapy, Speech Therapy and Nursing, University of Castilla-La Mancha, Talavera de la Reina, Toledo, Spain.

ABSTRACT

Objective: Muscular fitness levels have been associated with cardiometabolic risk in children, although whether body weight acts as a confounder or as an intermediate variable in this relationship remains controversial. The aim of this study was to examine whether the association between muscular fitness and cardiometabolic risk factors is mediated by body mass index (BMI).

Design and methods: Cross-sectional study using a sample of 1158 schoolchildren aged 8-11 years from the province of Cuenca, Spain. We measured anthropometrics and biochemical variables and we calculated a muscular fitness index as the sum of z-scores of handgrip dynamometry/weight and standing long jump, and we estimated a previously validated cardiometabolic risk index (CMRI). Linear regression models were fitted for mediation analysis to assess whether the association between muscular fitness and cardiometabolic risk was mediated by BMI.

Results: Children with normal weight (NW) had a better cardiometabolic risk profile than their overweight (OW) or obese (OB) peers after controlling for muscular fitness. Marginal estimated mean ± SE values for NW, OW and OB categories of CMRI were -0.75 ± 0.06 < 0.84 ± 0.10 < 2.18 ± 0.16 in boys and -0.73 ± 0.06 < 0.96 ± 0.10 < 2.71 ± 0.17 in girls, both p < 0.001. Children with higher levels of muscular fitness had a better cardiometabolic risk profile (CMRI marginal estimated mean ± SE 1.04 ± 0.13 > 0.05 ± 0.09 >-1.16 ± 0.13 for lower, middle and upper quartiles of muscular fitness in boys and 1.01 ± 0.16 > 0.10 ± 0.09 > -1.02 ± 0.15 in girls, both p < 0.001), but differences disappeared when controlling for BMI. BMI acted as a full mediator between muscular fitness and most cardiometabolic risk factors (Sobel test z = -11.44 for boys; z = -11.83 for girls; p < 0.001 in CMRI mediation model) and as a partial mediator in the case of waist circumference (Sobel test z=-14.86 for boys; z=-14.51 for girls; p<0.001).

Conclusions: BMI mediates the association between muscular fitness and cardiometabolic risk in schoolchildren. Overall, good muscular fitness is associated with lower cardiometabolic risk, but particularly when accompanied by normal weight.

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Related in: MedlinePlus

BMI mediation models of the relationship between muscular fitness and cardiometabolic risk variables, controlling for age, by sex.A: MAP; B: log fasting insulin; C: log TG/HDL-c; D: WC; E: CMRI. Data in roman type refer to boys. %Med: Percentage mediated by proposed mediator. Data in italics refer to girls. **p≤0.001; *p≤0.05.
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pone.0116506.g001: BMI mediation models of the relationship between muscular fitness and cardiometabolic risk variables, controlling for age, by sex.A: MAP; B: log fasting insulin; C: log TG/HDL-c; D: WC; E: CMRI. Data in roman type refer to boys. %Med: Percentage mediated by proposed mediator. Data in italics refer to girls. **p≤0.001; *p≤0.05.

Mentions: We tested BMI as a potential mediator of the relationship between MF and MAP (Fig. 1A). In the first regression equation MF was negatively associated with BMI (p≤0.001). In the second equation MF was also negatively associated with MAP (p≤0.001). Finally, in the third equation, with MF and BMI both included in the model BMI was positively associated with MAP (p≤0.001) and MF was positively associated with CMRI in boys and girls although the associations were not statistically significant. These results suggest that the effect of MF on MAP was fully mediated by BMI. Using the Sobel test for mediation it was estimated that in boys 14.5% (z=-7.93; p≤0.001) and in girls 15% (z=-7.89; p≤0.001) of the total effect of MF on MAP was mediated by BMI.


BMI as a mediator of the relationship between muscular fitness and cardiometabolic risk in children: a mediation analysis.

Díez-Fernández A, Sánchez-López M, Gulías-González R, Notario-Pacheco B, Cañete García-Prieto J, Arias-Palencia N, Martínez-Vizcaíno V - PLoS ONE (2015)

BMI mediation models of the relationship between muscular fitness and cardiometabolic risk variables, controlling for age, by sex.A: MAP; B: log fasting insulin; C: log TG/HDL-c; D: WC; E: CMRI. Data in roman type refer to boys. %Med: Percentage mediated by proposed mediator. Data in italics refer to girls. **p≤0.001; *p≤0.05.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4295865&req=5

pone.0116506.g001: BMI mediation models of the relationship between muscular fitness and cardiometabolic risk variables, controlling for age, by sex.A: MAP; B: log fasting insulin; C: log TG/HDL-c; D: WC; E: CMRI. Data in roman type refer to boys. %Med: Percentage mediated by proposed mediator. Data in italics refer to girls. **p≤0.001; *p≤0.05.
Mentions: We tested BMI as a potential mediator of the relationship between MF and MAP (Fig. 1A). In the first regression equation MF was negatively associated with BMI (p≤0.001). In the second equation MF was also negatively associated with MAP (p≤0.001). Finally, in the third equation, with MF and BMI both included in the model BMI was positively associated with MAP (p≤0.001) and MF was positively associated with CMRI in boys and girls although the associations were not statistically significant. These results suggest that the effect of MF on MAP was fully mediated by BMI. Using the Sobel test for mediation it was estimated that in boys 14.5% (z=-7.93; p≤0.001) and in girls 15% (z=-7.89; p≤0.001) of the total effect of MF on MAP was mediated by BMI.

Bottom Line: Muscular fitness levels have been associated with cardiometabolic risk in children, although whether body weight acts as a confounder or as an intermediate variable in this relationship remains controversial.BMI mediates the association between muscular fitness and cardiometabolic risk in schoolchildren.Overall, good muscular fitness is associated with lower cardiometabolic risk, but particularly when accompanied by normal weight.

View Article: PubMed Central - PubMed

Affiliation: Social and Health Care Research Center, University of Castilla-La Mancha, Cuenca, Spain; Faculty of Occupational Therapy, Speech Therapy and Nursing, University of Castilla-La Mancha, Talavera de la Reina, Toledo, Spain.

ABSTRACT

Objective: Muscular fitness levels have been associated with cardiometabolic risk in children, although whether body weight acts as a confounder or as an intermediate variable in this relationship remains controversial. The aim of this study was to examine whether the association between muscular fitness and cardiometabolic risk factors is mediated by body mass index (BMI).

Design and methods: Cross-sectional study using a sample of 1158 schoolchildren aged 8-11 years from the province of Cuenca, Spain. We measured anthropometrics and biochemical variables and we calculated a muscular fitness index as the sum of z-scores of handgrip dynamometry/weight and standing long jump, and we estimated a previously validated cardiometabolic risk index (CMRI). Linear regression models were fitted for mediation analysis to assess whether the association between muscular fitness and cardiometabolic risk was mediated by BMI.

Results: Children with normal weight (NW) had a better cardiometabolic risk profile than their overweight (OW) or obese (OB) peers after controlling for muscular fitness. Marginal estimated mean ± SE values for NW, OW and OB categories of CMRI were -0.75 ± 0.06 < 0.84 ± 0.10 < 2.18 ± 0.16 in boys and -0.73 ± 0.06 < 0.96 ± 0.10 < 2.71 ± 0.17 in girls, both p < 0.001. Children with higher levels of muscular fitness had a better cardiometabolic risk profile (CMRI marginal estimated mean ± SE 1.04 ± 0.13 > 0.05 ± 0.09 >-1.16 ± 0.13 for lower, middle and upper quartiles of muscular fitness in boys and 1.01 ± 0.16 > 0.10 ± 0.09 > -1.02 ± 0.15 in girls, both p < 0.001), but differences disappeared when controlling for BMI. BMI acted as a full mediator between muscular fitness and most cardiometabolic risk factors (Sobel test z = -11.44 for boys; z = -11.83 for girls; p < 0.001 in CMRI mediation model) and as a partial mediator in the case of waist circumference (Sobel test z=-14.86 for boys; z=-14.51 for girls; p<0.001).

Conclusions: BMI mediates the association between muscular fitness and cardiometabolic risk in schoolchildren. Overall, good muscular fitness is associated with lower cardiometabolic risk, but particularly when accompanied by normal weight.

Show MeSH
Related in: MedlinePlus