Associations of linear growth and weight gain in the first 2 years with bone mass at 4 years of age in children in Dhaka, Bangladesh

Objective: Growth faltering is widespread in many low- and middle-income countries, but its effects on childhood bone mass accrual are unknown. The objective of this study was to estimate associations between length (conditional length-for-age z-scores, cLAZ) and weight (conditional weight-for-age z-scores, cWAZ) gain in three age intervals (ages 0-6, 6-12 and 12-24 months) with dual-energy X-ray absorptiometry-derived measures of bone mass (total body less head (TBLH) bone mineral content (BMC), areal bone mineral density (aBMD) and bone area) at 4 years of age.

Design: Associations between interval-specific growth parameters (cLAZ and cWAZ) and bone outcomes were estimated using linear regression models, adjusted for maternal, child and household characteristics.

Setting: Data collection occurred in Dhaka, Bangladesh.

Participants: 599 healthy children enrolled in the BONe and mUScle Health in Kids Study.

Results: cLAZ in each age interval was positively associated with TBLH BMC, aBMD and bone area at 4 years; however, associations attenuated towards null upon adjustment for concurrent height-for-age z-scores (HAZ) at age 4 years and confounders. cWAZ from 0 to 6 and 6 to 12 months was not associated with bone mass, but every sd increase in cWAZ between 12 and 24 months was associated with greater BMC (7·6 g; 95 % CI: 3·2, 12·0) and aBMD (0·008 g/cm²; 95 % CI: 0·003, 0·014) after adjusting for concurrent WAZ, HAZ and confounders.

Conclusions: Associations of linear growth (birth to 2 years) with bone mass at age 4 years were explained by concurrent HAZ. Weight gain in the second year of life may increase bone mass independently of linear growth in settings where growth faltering is common.