TY - JOUR
T1 - Physical Activity and Bone Accretion
T2 - Isotemporal Modeling and Genetic Interactions
AU - Mitchell, Jonathan A.
AU - Chesi, Alessandra
AU - McCormack, Shana E.
AU - Cousminer, Diana L.
AU - Kalkwarf, Heidi J.
AU - Lappe, Joan M.
AU - Gilsanz, Vicente
AU - Oberfield, Sharon E.
AU - Shepherd, John A.
AU - Kelly, Andrea
AU - Grant, Struan F.A.
AU - Zemel, Babette S.
N1 - Funding Information:
We appreciate the dedication of the study participants and their families, and the support of Dr. Karen Winer, Scientific Director of the Bone Mineral Density in Childhood Study. The study was supported by funding from the National Institutes of Health (NIH), Grant Nos. R01HD58886 and UL1TR000077. The study was also supported by Eunice Kennedy Shriver National Institute of Child Health and Human Development contracts: N01-HD-1-3228, -3329, -3330, -3331, -3332, and -3333. Jonathan Mitchell was support by National Institutes of Health grant K01HL123612. The results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation.
Publisher Copyright:
© 2018 by the American College of Sports Medicine.
PY - 2018/5/1
Y1 - 2018/5/1
N2 - Purpose This study aimed to determine if replacing time spent in high- and low-impact physical activity (PA) predicts changes in pediatric bone mineral density (BMD) and content (BMC). Methods We analyzed data from the longitudinal Bone Mineral Density in Childhood Study (N = 2337 with up to seven visits). The participants were age 5-19 yr at baseline, 51.2% were female, and 80.6% were nonblack. Spine, total hip, and femoral neck areal BMD and total body less head (TBLH) BMC Z-scores were calculated. Hours per day spent in high- and low-impact PA were self-reported. Standard covariate-adjusted (partition model) and time allocation-sensitive isotemporal substitution modeling frameworks were applied to linear mixed models. Statistical interactions with sex, self-reported ancestry, age, and bone fragility genetic scores (percentage of areal BMD-lowering alleles carried) were tested. Results In standard models, high-impact PA was positively associated with bone Z-score at all four skeletal sites (e.g., TBLH-BMC Z-score: beta = 0.05, P = 2.0 × 10-22), whereas low-impact PA was not associated with any of the bone Z-scores. In isotemporal substitution models, replacing 1 h·d-1 of low- for high-impact PA was associated with higher bone Z-scores (e.g., TBLH-BMC Z-score: beta = 0.06, P = 2.9 × 10-15). Conversely, replacing 1 h·d-1 of high- for low-impact PA was associated with lower bone Z-scores (e.g., TBLH-BMC Z-score: beta = -0.06, P = 2.9 × 10-15). The substitution associations were similar for each sex and ancestry group, and for those with higher and lower genetic scores for bone fragility (P-interactions > 0.05), but increased in strength among the older adolescents (P-age interactions < 0.05). Conclusions Time-sensitive models suggest that replacing low-impact PA for high-impact PA would be beneficial for the growing skeleton in the majority of children.
AB - Purpose This study aimed to determine if replacing time spent in high- and low-impact physical activity (PA) predicts changes in pediatric bone mineral density (BMD) and content (BMC). Methods We analyzed data from the longitudinal Bone Mineral Density in Childhood Study (N = 2337 with up to seven visits). The participants were age 5-19 yr at baseline, 51.2% were female, and 80.6% were nonblack. Spine, total hip, and femoral neck areal BMD and total body less head (TBLH) BMC Z-scores were calculated. Hours per day spent in high- and low-impact PA were self-reported. Standard covariate-adjusted (partition model) and time allocation-sensitive isotemporal substitution modeling frameworks were applied to linear mixed models. Statistical interactions with sex, self-reported ancestry, age, and bone fragility genetic scores (percentage of areal BMD-lowering alleles carried) were tested. Results In standard models, high-impact PA was positively associated with bone Z-score at all four skeletal sites (e.g., TBLH-BMC Z-score: beta = 0.05, P = 2.0 × 10-22), whereas low-impact PA was not associated with any of the bone Z-scores. In isotemporal substitution models, replacing 1 h·d-1 of low- for high-impact PA was associated with higher bone Z-scores (e.g., TBLH-BMC Z-score: beta = 0.06, P = 2.9 × 10-15). Conversely, replacing 1 h·d-1 of high- for low-impact PA was associated with lower bone Z-scores (e.g., TBLH-BMC Z-score: beta = -0.06, P = 2.9 × 10-15). The substitution associations were similar for each sex and ancestry group, and for those with higher and lower genetic scores for bone fragility (P-interactions > 0.05), but increased in strength among the older adolescents (P-age interactions < 0.05). Conclusions Time-sensitive models suggest that replacing low-impact PA for high-impact PA would be beneficial for the growing skeleton in the majority of children.
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U2 - 10.1249/MSS.0000000000001520
DO - 10.1249/MSS.0000000000001520
M3 - Article
C2 - 29465475
AN - SCOPUS:85045455907
VL - 50
SP - 977
EP - 986
JO - Medicine and Science in Sports and Exercise
JF - Medicine and Science in Sports and Exercise
SN - 0195-9131
IS - 5
ER -