Physical activity, bone mineral density, and bone mineral content in young adult women

Exposures during childhood that affect bone mineral density (BMD) and bone mineral content (BMC) could have long-term effects on osteoporosis development and associated fracture risk. We evaluated associations of physical activity in late childhood, adolescence, and in young adulthood with young adult BMD and BMC using data from the Dietary Intervention Study in Children (DISC) and DISC06 Follow-up Study. Moderate/Intense physical activity (MET hours/week) was assessed by questionnaire on five occasions during childhood/adolescence and again during young adulthood. BMD and BMC were measured by dual energy x-ray absorptiometry (DEXA) scans during young adulthood. Linear mixed models were used to analyze the association of physical activity with BMD and BMC during young adulthood. Generalized linear latent affects mixed models were used to evaluate the association of the latent variable "childhood physical activity" with BMD and BMC in young adulthood. Young adult BMC and BMD increased with increasing physical activity during young adulthood after adjustment for body weight, although the test for trend was significant only for BMD. Young adult BMC increased significantly with increasing physical activity during youth. Promotion of physical activity in youth and young adulthood could potentially decrease the magnitude of osteoporosis in older women as a public health problem, but more research is needed.