The influence of body weight and composition, pubertal status, tobacco use and exposure, physical activity and muscle strength on bone mass of Chinese adolescent

Although much has been learned about osteoporosis occurring later in life, large sample population studies are needed to assess potentially critical relationships between body weight, pubertal status, tobacco use and exposure, physical activity, and strength on bone mass in early life. Understanding these relationships during the growing years is critical, since optimizing peak bone mass is the most powerful preventive strategy for osteoporosis.;To address these issues, we measured heel and forearm bone mass of 466 Chinese adolescents ranging in age between 10 and 16 years. We measured bone mineral density (BMD) and content (BMC) using dual-energy x-ray absorptiometry and grip strength by isometric dynamometry. We estimated percent fat, fat mass and lean mass by bioelectrical impedance analysis and determined pubertal status, active and passive smoking, and physical activity using questionnaire data.;By performing multiple linear regression models, we determined that 32% of the variance in forearm BMC of the girls was attributed to weight, 6% to strength, and 4% to pubertal status for a combined variance of 42%. In boys, 36% of the variance in forearm BMC was attributed to strength, and 6% to body weight, for a combined variance of 42%. Heel BMC was best predicted by weight (21% in girls; 46% in boys) and strength (3% in girls; 1% in boys) accounting for 24% of the variability in girls and 47% in boys.;We failed to find significant inverse relationships between smoking and bone mass in this cross-sectional study. The reasons may have been due to the low levels and duration of tobacco use and exposure among the adolescents we studied. Nevertheless, we believe that this is the first study that investigated the role of smoking on bone mass during adolescence.;Our findings support the influence of body weight, pubertal status, and muscle strength on bone acquisition during adolescence. We conclude that the processes that determine fracture risk in adulthood and increase the likelihood of osteoporosis, begin during childhood and adolescence.