We conducted a survey on bone mineral density of adult males living in Japan , for the pur pose of clarifying the differences in factors that affect bone mineral density among different age groups and contribute to prevention of osteoporosis. Bone mineral densities of 916 men aged 20 to 69 were measured by dual energy X-ray absorptiometry and their lifestyle was examined. The relationship of bone mineral density with BMI (body mass index) and lifestyle factors was examined by applying to the

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... n value for each item by the unpaired t-test or one-way ANOVA. Multiple regression analysis, in which the bone mineral density was treated as the dependent variable and BMI and lifestyle factors as the independent variables, was applied to evaluate the effects of them. In the age group of 20-29 years old, BMI (p<0.01) and exercise habit at present (p<0.05) were significantly positively associated with bone mineral density. In the age group of 30-39 years old, the positive association of bone mineral density with BMI was observed (p<0.01). In the age group of 40-49 years old, bone mineral density was significantly positively associated with BMI (p<0.01), exercise habit (at present) (p<0.05), exercise habit (in the past) (p<0 .05), and intake of dairy products (in the past) (p<0.01). In the age groups of 50 years and over , bone mineral density was significantly positively associated with BMI and smoking habit (p<0 .01). According to the results of this study, the health education for encouraging exercise and intake of dairy products from younger age up to 40s was considered to be effective for primary prevention of osteoporosis. However, it seems plausible that such education is less effective for the individuals aged 50 or more.