Exercise, smoking, and calcium intake during adolescence and early adulthood as determinants of peak bone mass

Abstract

Objective : To evaluate the contribution to peak bone mass of exercise, smoking, and calcium intake in adolescents and young adults. Design : Prospective cohort study with end point measurement (bone mineral density) after 11 years'20follow up for lifestyle. Setting : Five university hospital clinics. Subjects : 264 (153 females, 111 males) subjects aged 9 to 18 years at the beginning of the follow up20and 20 to 29 years at the time of measurement of bone mineral density. Main outcome measure : Bone mineral density of lumbar spine and femoral neck by dual energy x ray absorptiometry; measures of physical activity and20smoking and estimates of calcium intake repeated three times during follow up. Results : In the groups with the lowest and highest20levels of exercise the femoral bone mineral densities (adjusted for age and weight) were 0.918 and 0.988 g/cm 2 for women (P=0.015), analysis of covariance) and 0.943 and 1.042 g/cm 2 for men (P=0.005), respectively; at the lumbar spine the respective20values were 1.045 and 1.131 (P=0.005) for men. In men the femoral bone mineral densities (adjusted for age, weight, and exercise) were 1.022 and 0.923 g/cm 2 for the groups with the lowest and highest values of smoking index (P=0.054, analysis of covariance). In women the adjusted femoral bone mineral density increased by 4.7% together with increasing calcium intake (P=0.089, analysis of covariance). In multiple regression analysis on bone mineral density of the femoral neck, weight, exercise, age, and smoking were independent predictors for men; with weight, exercise, and age for women. These predictors together explained 38% of the variance in bone mineral density in women and 46% in men. At the lumbar spine, weight, smoking, and exercise were predictors for men; and only weight for women. Conclusions : Regular exercise and not smoking is important in achieving maximal peak bone mass in adolescents and young adults.