Factors affecting bone mineral density in high school girls

Abstract

Objectives: first to establish a local normal range for hip and spine bone density in the teenage years. Secondly to determine what factors might affect bone mineral density at this age.

Methods: bone mineral density (DPX absorptiometer) at the hip and spine in a cohort of 138 high school girls; mean age 16.4 yr (SD 0.34). Anthropometric factors, calcium intake, physical activity and other lifestyle and medical data were documented in each subject.

Results: in this group of 16 year old schoolgirls mean bone mineral density at the hip, 1.01 (0.13) was not significantly different from 20-25 year old New Zealand females, but bone mineral density at lumbar spine, 1.17 (0.12), was significantly lower. Positive correlations of bone mineral density with weight, height, physical activity and calcium intake were demonstrated. Weight was clearly the best predictor of bone mineral density variability. Calcium intake and physical activity showed no predictive value at the spine but contributed significantly at all regions of the femur and particularly at the trochanter.

Conclusions: it appears that peak bone mass can be modified by nutrition and exercise. Adolescents should be encouraged into regular exercise programmes and to maintain adequate body mass and calcium intakes.