[Cross-sectional study of factors related to Achilles bone mineral density measured by an ultrasound system]

A cross-sectional study was conducted to examine the relationship between bone mineral density (BMD) and life-style related factors including exercise and dietary habits in 1016 pre-menopausal women and 856 post-menopausal women in Ishikawa Prefecture, Japan. The achilles BMD in 1,872 women ages between 19 and 85 years were measured from 1995 to 1996 by an ultrasound system. The stiffness index calculated by the Lunar Achilles ultrasound machine was used as the BMD in this analysis. Self-administered questionnaires were used to obtain the following information: medical history, pregnancy, delivery and menstrual history, height at 20-years of age, present number of teeth, fracture history, sports exercise history, food intake frequency, smoking and drinking history, and daily physical activity. Analysis of covariance and multiple regression analysis were performed to evaluate the contribution of life-style related factors to BMD after adjustment for age and BMI (Body mass index) in pre- and post-menopausal women, respectively. Results were as follow: 1) BMD was inversely associated with increasing age in pre- and post-menopausal women. The BMD level of post-menopausal women were lower than that of pre-menopausal women in each 5-year age group. The pearson's correlatin coefficient between age and BMD was significant at -0.25 and -0.44 in pre- and post-menopausal women, respectively. 2) Body mass index (BMI) and BMD were positively correlated in pre- and post-menopausal women. 3) In pre-menopausal women, lower BMD was associated with the following factors: age, lower BMI, no history of joining a sports club in junior high school, absence of current regular sports, being inactive in daily life, having joint pains, lower number of remaining teeth and lower dairy product intake. 4) In post-menopausal women, lower BMD was associated with the following factors: age, lower BMI, no history of joining a sports club in junior high school, past history of fracture and longer post-menopausal years. Factors associated with lower BMD in this study were regarded as risk factors for future osteoporotic fractures in the elderly, or signs of lower BMD. Therefore, the information of these factors should be employed in health education for the prevention of osteoporosis. Especially, participating in a sports club while in junior high school may be a recommendation for acquiring higher BMD even in the post-menopausal period.