Does Stage of Sexual Maturation Determine the Relationship of Calcium Intake and Physical Activity to Bone Mass Accrual
Category: Bone Acquisition and Pediatric Bone Disease
Oral Presentations, Presentation Number: 1072
Session: Concurrent Oral Session 12: Bone Acquisition and Pediatric Bone Disease
Saturday, October 13, 2012 3:30 PM - 3:45 PM, Minneapolis Convention Center, Room 200DE
* Joan Lappe, Creighton University Osteoporosis Research Center, USA, Babette Zemel, Children's Hospital of Philadelphia, Patrice Watson, Creighton University, USA, Xiang Fang, Creighton University, USA, Vicente Gilsanz, Children's Hospital Los Angeles, USA, Heidi Kalkwarf, Cincinnati Children's Hospital Medical Center, USA, Sharon Oberfield, Columbia University Medical Center, USA, John Shepherd, University of California, San Francisco, USA, Karen Winer, National Institutes of Health, USA
Background: Although it is accepted that dietary calcium (Ca) and physical activity (PA) increase bone mass accrual, evidence is lacking about whether Ca and/or PA might be more important for accrual during specific stages of sexual maturation.
Aim: To describe the relationship between Ca and PA and total body bone mineral content (TBBMC) accrual by Tanner stage (TS) in a large, multi-racial cohort of children followed prospectively from early childhood until sexual maturity.
Methods: Five U.S. centers recruited 2014 healthy children (ages 5 to 19 yr) and measured them annually for up to 7 yrs. Subjects with at least 2 visits are included in this analysis (915 males, 835 females). TBBMC was assessed by dual energy x-ray absorptiometry, height (ht) with a stadiometer, and TS by endocrinologist exam. PA and Ca were assessed by self-report using the modified Slemenda questionnaire and a food frequency questionnaire, respectively.
Analyses: The relationship between PA (hrs/wk) and Ca (mg/d) and TBBMC was assessed using linear regression in a mixed model. Specifically, annualized TBBMC change (from the prior visit) was modeled as a function of prior visit TBBMC, annualized ht change, TS, and PA/Ca. Separate regressions evaluated the significance of TS by PA/Ca interactions performed on gender and racial (black, B/nonblack, NB) subgroups.
Results: Males have significantly greater average PA and Ca than females, while B have greater PA and lower Ca than NB. PA was a significant predictor of TBBMC accrual in all subgroups except B males, but no differences were seen among TS. Ca significantly predicted accrual in NB , but not in B. When analyzing by TS, Ca was a significantly better predictor of accrual in TS 3 and 4 in NB males, in TS4 in B males, and in TS4 and 5 in NB females. When controlling for Ca, PA was associated with TBBMC accrual in all subgroups except for B males (p<0.08). When controlling for PA, Ca was significantly associated with accrual only for NB.
Conclusion: PA contributes significantly to bone mass accrual in this large cohort, but has no significant association with any specific stage of sexual maturation. Overall, Ca is significantly associated with accrual in NB only, both males and females. Within subgroups, Ca appears to be more important for accrual during specific stages of sexual maturation, ie, B males, TS4; NB males, TS3 and 4, and NB females, later stages of sexual maturation.
* Presenting Authors(s): Joan Lappe, Creighton University Osteoporosis Research Center, USA