[A study of bone density and lifestyles of high school girls]

To obtain basic data on the bone density of high school girls, the bone density of the right heel was measured in principle and their lifestyles were surveyed. The subjects were 142 girls (15-18 years, mean +/- SD = 16.5 +/- 0.8 years old) of a high school in Nagano Prefecture, who accepted our visiting bone health check. Bone density was measured with an 'Achilles' ultrasound bone-densitometer (Lunar Co.) and a self-registered questionnaire on their lifestyles was also employed in this study. The main results were as follows: 1. There were no significant correlations between Stiffness and, age, grade, bone fracture, family history, and regularity of menstruation. However, Stiffness significantly correlated to the age of menophania (r = -0.191, p = 0.002) 2. High school girls who belonged to a sports club had significantly higher bone density than other girls. Those who did-exercises which consist mainly of jumping, had significantly higher bone density than others who participated in running sports or did no exercise. There were also significant differences in the frequency of exercise and the duration of exercise. Moreover, those who had a regular exercise history had higher bone density than those who had no regular exercise history, and the mean Stiffness of the group that did exercises daily was higher than for those who did not. 3. There were no significant correlations between Stiffness and food intakes. There also were no significant difference for Stiffness concerning intake of calcium-containing food groups. Regarding the cause of weight loss of more than 2 kg/month, the mean Stiffness of the group with intense exercise was significantly higher than those in the no-weigh loss group and the group that had reduced dietary intake. 4. Regarding the relationships between bone density and the lifestyles of high school girls, a delayed age of menophania had a significantly decreasing effect on Stiffness, whereas three variables of regular exercise habits at present, body weight, and exercise histories had significantly increasing effects on Stiffness in multiple regression analysis. 5. It is considered that there may be other important factors in the relationship between bone density and lifestyle of adolescent females who are in a developmental state. Therefore, the measurement of bone density and its assessment need consideration from points of view which are different from those for middle-aged and the elderly people.