Bone Abstracts

Recent evidence supports a strong influence of early life movement on infant bone strength. However, it is not known whether early motor development also influences bone strength in later life. Therefore, we examined relationships between locomotor score (using components of the Denver Developmental Screening Test) at 18 months, and the Avon Longitudinal Study of Parents and Children (ALSPAC) Co-ordination Test (ACT) score at 7 years, and bone outcomes as measured at age 17 years, in 3810 ALSPAC participants. Total hip bone mineral density (BMD) was assessed from dual-energy X-ray absorptiometry (DXA), and periosteal circumference (PC), cortical thickness (CT), cortical bone area (CBA), cortical BMD (BMD_C) and cross sectional moment of inertia (CSMI) by peripheral quantitative computed tomography (pQCT) at the 66% tibial site. Positive relationships were observed between 18 month and 7 year motor scores, and hip BMD (0.075 (0.072, 0.078) and 0.088 (0.053, 0.124)), PC (0.085 (0.016, 1.108) and 0.056 (0.030, 0.083)), CT (0.089 (0.061, 0.118) and 0.050 (0.020, 0.081)), CBA (0.098 (0.074, 0.123) and 0.064 (0.036, 0.092)) and CSMI (0.098 (0.059, 0.105) and 0.065 (0.039, 0.092)) (standardized beta coefficients (95% CI) for associations with 18 month and 7 year motor development score respectively, adjusted for sex, age at exposure/outcome, maternal social class, birthweight and gestation age (P<0.001 for all associations)). Equivalent associations were not seen for BMD_C (P=0.52 and 0.22 for locomotor and ACT score respectively). Gender×motor score interactions were observed for hip BMD and tibia CA and CSMI (all P<0.01) with regression coefficients greater in males. In further analyses intended to explore the role of body composition in mediating these relationships, positive associations with hip BMD and pQCT parameters were attenuated by adjustment for height, fat and lean mass at 17 years (36–82% reduction). In conclusion, early life motor development is positively related to skeletal development as measured at age 17, particularly in boys, reflecting both greater periosteal expansion and reduced endosteal expansion, resulting in greater predicted bone strength. Changes in body composition may play a role in mediating these relationships between early motor development and subsequent bone development, possibly reflecting altered levels of physical activity.

Disclosure: The authors declared no competing interests.