Bone Mass in Schoolchildren in Brazil: the Effect of Racial Miscegenation, Pubertal Stage, and Socioeconomic Differences

The purpose of this study was to evaluate bone mass by phalanges ultrasound in healthy white and black schoolchildren in relationship to socioeconomic level, pubertal stage, and body composition. Included were 1,356 healthy schoolchildren aged from 6 to 11 years from different socioeconomic levels and both genders; all were placed into white and black groups. Weight, height, body mass index, fat percentage, fat mass, and lean mass were evaluated by anthropometric methods, and AD-SoS bone quantity and UBPI bone quality were evaluated using a third-generation IGEA phalanges DBM Sonic BP ultrasound. Data were compared using the Mann-Whitney, chi-squared, correlation coefficient, and analyses of multiple linear regression statistical tests with 5% significance. Black schoolchildren predominated in the low socioeconomic levels. Higher values of weight and height for black boys and girls were observed in the lean mass in relation to white children of the same gender and age. An increasing variation in the bone quantity mean was observed from 6 to 11 years of age and with pubertal stage for both genders and skin color. The white schoolchildren presented higher values of bone quantity and quality in relation to the black children. The anthropometric, gender, and socioeconomic level variables explained only 16 and 11% of the variability of bone quantity and quality, respectively. As such, the present study, carried out with healthy black and white Brazilian schoolchildren, demonstrated higher bone mass, as evaluated by ultrasound, in white than in black schoolchildren.