Beat osteoporosis - nourish and exercise skeletons (BONES): a group randomized controlled trial in children

Abstract

Background: Lifelong healthy habits developed during childhood may prevent chronic diseases in adulthood. Interventions to promote these habits must begin early. The BONES (Beat Osteoporosis - Nourish and Exercise Skeletons) project assessed whether early elementary school children participating in a multifaceted health behavior change, after-school based intervention would improve bone quality and muscular strength and engage in more bone-strengthening behaviors.

Methods: The 2-year BONES (B) intervention included bone-strengthening physical activity (85 min/week), educational materials (2 days/week), and daily calcium-rich snacks (380 mg calcium/day) delivered by after-school program leaders. BONES plus Parent (B + P) included an additional parent education component. From 1999 to 2004, n = 83 after-school programs (N = 1434 children aged 6-9 years) in Massachusetts and Rhode Island participated in a group randomized trial with two intervention arms (B only, n = 25 programs; B + P, n = 33) and a control arm (C, n = 25). Outcome measures (primary: bone quality (stiffness index of the calcaneus) and muscular strength (grip strength and vertical jump); secondary: bone-strengthening behaviors (calcium-rich food knowledge, preference, and intake; and physical activity level (metabolic equivalent time (MET) score, and weight-bearing factor (WBF) score)) were recorded at baseline, and after years one and two. Analyses followed an intent-to-treat protocol, and focused on individual subjects' trajectories along the three time points adjusting for baseline age and race via a mixed-effects regression framework. Analyses were performed with and without sex stratification.

Results: Children in B + P increased bone stiffness compared to C (p = 0.05); No significant changes were observed in muscle strength, food knowledge, or vertical jump. Children in B + P showed significant improvement in their MET and WBF scores compared to C (p < 0.01) with a stronger effect in boys in both B and B + P (all p < 0.01).

Conclusion: After-school programs, coupled with parental engagement, serving early elementary school children are a potentially feasible platform to deliver bone-strengthening behaviors to prevent osteoporosis in adulthood, with some encouraging bone and physical activity outcomes.

Trial registration: ClinicalTrials.gov NCT00065247. Retrospectively registered. First posted July 22, 2003.

Keywords: Bone; Calcium; Child; Health behavior; Osteoporosis; Randomized controlled trial; Weight loading physical activity.

Fig. 1

The BONES Project theoretical framework. The theoretical framework integrated existing constructs and prior research to identify (1) Behavioral; (2) Communications and Educational; and (3) Environmental behavior change strategies to influence (a) personal; (b) parental/caregiver, and (c) societal influences on child health behavior. Influencing factors szhown in red were targeted by the intervention

Fig. 2

Flow diagram of recruitment and analysis in the BONES Project. Note: n = number of after-school programs; N = number of children

Fig. 3

Mean adjusted changes in WBF score, MET score, and bone stiffness by group^a. Abbreviations: WBF, weight-bearing factor; MET, metabolic equivalent time; C, Control; B, BONES; B + P, BONES + Parent; CI, confidence interval. ^aMixed effects regression model adjusted for time point, baseline age, and race/ethnicity (white, black, Hispanic, others); and adjusted for individual nested within after-school program as cluster effects. ^bError bars represent 95% confidence intervals derived from standard error. ^cCIs that do not cross y = 0 indicate the mean change is significantly different from 0