BONE-MINERAL DENSITY BY SINGLE-PHOTON X-RAY ABSORPTIOMETRY IN CHILEANCHILDREN AND ADOLESCENTS

Objective. To assess bone mineralization in healthy Chilean children a nd adolescents, considering sex, age, height, and puberty. Methods. In a descriptive cross sectional study, the appendicular bone mineral de nsity (BMD) was measured by single photon x-ray absorptiometry at dist al (D-BMD) and ultradistal (UD-BMD) regions of the forearm, in 571 hea lthy children and adolescents of Valparaiso and Vina del Mar, Chile, c onsidering their age, sex, height, calcium intake, and pubertal develo pment according to Tanner. Results. Physical activity was regular; dai ly average calcium intake was 580 +/- 100 mg and the D-BMD and UD-BMD showed a 3 step growth pattern: Slow increments between 4 and 8 years of age in girls (r = 0.07 and r = 0.37, respectively) and between 4 an d 12 years in boys (r = 0.17 and r = 0.39); sharp increases between 8 and 19 years in female adolescents (r = 0.78 and r = 0.73) and between 12 and 20 years in male adolescents (r = 0.82 and r = 0.67); and dece leration of growth from 19 years in female adolescents and 20 years in males. Considering Tanner classifications (T), boys had significant d ifferences in mean D-BMD between T3 and T4 (p < 0.001) and between T4 and T5 (p < 0.001) and in mean UD-BMD between T3 and T4 (p < 0.001). T hey achieve higher values than women in adulthood. Girls showed signif icant differences in mean D-BMD between T3 and T4 (p = 0.003) and T4 a nd T5 (p < 0.001), and in mean UD-BMD between T3 and T4 (p = 0.016). C onsidering menarche, there was an important increment in bone mass up to 3 years after menarche, and it was significant until 2 years after for D-BMD (p < 0.02) and 1 year after for UD-BMD (p < 0.001). In girls and boys, bone mass increments did not correlate with height incremen ts. A delay in bone mass increments was observed at early Tanner stage s. Conclusion. Between 4 and 8 years in girls and 4 and 12 years in bo ys, there is a slow increment in bone density correlated with age and sex. A steeper slope in bone growth started with puberty, correlated w ith Tanner stage. Bone mineral increments did not correlate with heigh t increments. At the end of pubertal development bone acquisition slow ed down. Men achieved higher bone density values than women.