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

Abstract

To evaluate the contribution to peak bone mass of exercise, smoking, and calcium intake in adolescents and young adults. Prospective cohort study with end point measurement (bone mineral density) after 11 years' follow up for lifestyle. Five university hospital clinics. 264 (153 females, 111 males) subjects aged 9 to 18 years at the beginning of the follow up and 20 to 29 years at the time of measurement of bone mineral density. Bone mineral density of lumbar spine and femoral neck by dual energy x ray absorptiometry; measures of physical activity and smoking and estimates of calcium intake repeated three times during follow up. In the groups with the lowest and highest levels of exercise the femoral bone mineral densities (adjusted for age and weight) were 0.918 and 0.988 g/cm2 for women (P = 0.015, analysis of covariance) and 0.943 and 1.042 g/cm2 for men (P = 0.005), respectively; at the lumbar spine the respective values 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/cm2 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. Regular exercise and not smoking is important in achieving maximal peak bone mass in adolescents and young adults.