Linear growth and relative weight gain in childhood and bone mass in adolescence: findings from the Pelotas (Brazil) 2004 birth cohort.

Abstract

To investigate independent relationships of linear growth and relative weight gain during defined periods of infancy, childhood, and early adolescence with areal bone mineral density (aBMD) of three sites at 11years. Data on weight and length/height were obtained at birth, 3, 12, and 24months, and the ages of 4, 6, and 11. The outcome was whole body, femoral neck, and lumbar spine aBMD (g/cm2) measured at 11years using dual-energy X-ray absorptiometry. The effects of weight gain and linear growth were analyzed using conditional relative weight and conditional length/height. Associations between conditional growth and outcomes were analyzed using linear regression, adjusted for multiple confounders. Individuals with data available for exposures and bone outcomes were 2875 and comprised the sample. For boys, the greatest magnitude of increase for whole body and height gain was at 48months (β 0.014, 95% CI 0.010; 0.018). For girls, higher aBMD was observed for those with greater height gain at 11years, representing for lumbar spine an increase of 0.056g/cm2 (95% CI 0.050; 0.062). For body weight, among boys, the greatest magnitude in the whole body was also associated with weight gain at 48months (β 0.014, 95% CI 0.010; 0.018). For girls, the highest coefficient was at 24months, representing for lumbar spine an increase of 0.028g/cm2, (95% CI 0.021; 0.035). Positive associations were demonstrated between length/height and weight gain and aBMD in both sexes, with emphasis on girls' aBMD in response to the linear growth achieved mainly at 11years.