Lifetime physical activity and calcium intake related to bone density in young women.
OBJECTIVE
Osteoporosis is a significant public health problem associated with increased mortality and morbidity. Our aim in this cross-sectional study was to investigate the relationship between lifetime physical activity and calcium intake and bone mineral density (BMD) and BMC (bone mineral content) in 42 regularly menstruating Caucasian women (age 21.26+/-1.91 years, BMI 23.83+/-5.85).


METHODS
BMD and BMC at the lumbar spine (L2-L4), hip (femoral neck, trochanter, total), and total body were assessed by dual energy x-ray absorptiometry (DXA). Lifetime history of physical activity and calcium intake was obtained by a structured interview using valid and reliable instruments.


RESULTS
Measures of both lifetime physical activity and calcium intake were highly correlated. In stepwise multiple regression analyses, lean mass was the most important and consistent factor for predicting BMD and BMC at all skeletal sites (attributable r2 = 28.8%-78.7%). Lifetime physical activity contributed to 3.0% of the variation in total body BMD, and life-time weight-bearing physical activity explained 15.1% of variance in lumbar spine BMC. Current calcium intake predicted 6% of the variance in BMD at the femoral neck and trochanter.


CONCLUSIONS
We found lean mass to be a powerful predictor of BMD and BMC in young women. Because lean mass can be modified to some extent by physical activity, public health efforts must be directed at increasing physical activity throughout the lifespan. Furthermore, our results suggest that adequate calcium intake may help to enhance bone mass, thus decreasing the risk of osteoporotic fracture later in life.
Wallace
Lorraine Silver
LS
Department of Family Medicine, The University of Tennessee Graduate School of Medicine, Knoxville 37920, USA.
Ballard
Joyce E
JE
D000328:Adult; D015992:Body Mass Index; D015519:Bone Density / Q000502:physiology*; D002136:Calcium, Dietary / Q000008:administration & dosage*; D003276:Contraceptives, Oral / Q000009:adverse effects; D003430:Cross-Sectional Studies; D015444:Exercise / Q000502:physiology*; D005260:Female; D050723:Fractures, Bone / Q000150:complications; D006801:Humans; D008572:Menarche / Q000502:physiology; D010024:Osteoporosis / Q000209:etiology* / Q000517:prevention & control*; D012044:Regression Analysis; D012189:Retrospective Studies; D012307:Risk Factors; D012680:Sensitivity and Specificity; D012907:Smoking / Q000009:adverse effects; D013223:Statistics as Topic / Q000379:methods; D013472:Sunlight; D011795:Surveys and Questionnaires; D016474:Weight-Bearing / Q000502:physiology
D002136:Calcium, Dietary; D003276:Contraceptives, Oral