Lower femoral neck bone mineral density in prepubertal former preterm girls

The purpose of this case-control study was to determine bone mineral conten t and areal bone mineral density at various skeletal sites in former preter m girls, aged 7-9 years, and to compare these data with age-matched term co ntrols. Subjects included 25 white, prepubertal, former preterm girls (gest ational age 30.8 +/- 0.3 weeks, birthweight 1461 +/- 56 g [mean +/- SEM]). Controls included 50 healthy, white, prepubertal girls born at term and mat ched for age (two controls per case). Measurements included anthropometrie variables, calcium intake according to a food-frequency questionnaire, bone mineral content (BMC; grams), and areal bone mineral density (aBMD; grams per square centimeter), using dual-energy X-ray absorptiometry (DXA) at six skeletal sites. Thirteen preterm girls and 13 age-matched term controls we re reassessed 1 year after the first DXA measurement. The former preterm gi rls were similar to controls in terms of age and height, but were lighter ( 24.6 +/- 0.6 vs. 27.0 +/- 0.6 kg, p = 0.02). They also reported a higher me dian calcium intake (1058 vs. 759 mg/day,p = 0.004). aBMD was lower in form er preterms compared with controls at the level of the radial metaphysis (0 .283 +/- 0.006 vs. 0.298 +/- 0.004, p = 0.04), femoral neck (0.593 +/- 0.01 1 vs. 0.638 +/- 0.010, p = 0.007), and total hip (0.596 +/- 0.012 vs. 0.640 +/- 0.010,p = 0.007), but was similar between the two groups at the radial diaphysis (0.437 +/- 0.004 vs. 0.436 +/- 0.004) and femoral diaphysis (1.0 26 +/- 0.015 vs. 1.030 +/- 0.011). Femoral neck aBMD remained lower compare d with controls in the subgroup of preterm girls reassessed after 1 year (0 .608 +/- 0.017 vs. 0.672 +/- 0.020, p = 0.02). In random effects models for longitudinal data, taking into account the effects of age, weight, and hei ght on aBMD (dependent variable), femoral neck aBMD remained lower in forme r preterms (p < 0.001). Prepubertal former preterm girls showed growth reco very, but had lower aBMD at the hip and radial metaphysis than age-matched term controls, despite spontaneously higher calcium intake. Preterm girls h ad similar aBMD results compared with controls at sites with predominantly cortical bone (radial and femoral diaphysis), which are known to be more se nsitive to calcium intake. (C) 2001 by Elsevier Science Inc. All rights res erved.