Physical activity is a prognostic factor for bone mineral density in Mexican children

Background. Bone mass is similar in pre-pubertal girls and boys and double in both genders between the onset of puberty and early adult life. Exogenous factors such as nutrition and exercise contribute to the acquisition of bone mass. The objective of this project was to correlate calcium intake and level of physical activity with bone mineral density (BMD) in a sample of Mexican school-age children. Methods. A validated questionnaire was applied. The questionnaire included the following dimensions: (a) sociodemographic information, (b) type of sports and games that involved physical activity and hours per week dedicated to them, (c) inactivity measured by hours expended watching TV or playing videogames per day and (d) dietary calcium. After completing the questionnaire, the children were invited to have a BMD and total body composition assessment using a dual-energy x-ray absorptiometry (DXA) (Prodigy LUNAR). Results. In this cross-sectional study, 212 children were included, 48.6% were girls. The average total BMD in boys and girls was 0.8805 ± 0.056 g/cm2 and 0.8788 ± 0.056g/cm2, respectively, with significant differences in the groups of 10and 12-year-old girls. An average of 10.9 ± 6.48 h of weekly physical activity was reported in boys and 10.6 ± 7.31 h in girls. Number of glasses of milk consumed was reported (1.7 ± 0.95 and 1.33 ± 0.91) per day in boys and girls, respectively. Differences in BMD in 10and 12-year-old girls adjusted according to menarche were found. In the linear regression analysis, lean body mass was significantly associated with total, L2-L4, pelvis, and forearm BMD. Physical activity was significantly associated with leg BMD and age was associated with pelvis and forearm BMD. Conclusions. High lean body mass, menarche and regular intense physical activity are predictors for a higher BMD in school-age children in Mexico City.