Relationship between Weight, Body Mass Index and Bone Mineral Density of Lumbar Spine in Women

OBJECTIVES: This study aims to identify a relationship between bone mineral density (BMD) of lumbar spine, and the weight and body mass index (BMI) in women. METHODS: The subjects were 1,143 females who visited the public health center. BMD (T-score), height and weight were measured and age, menopause, diabetes and hypertension, exercising status and smoking status were inquired by interview. RESULTS: Among the subjects, 362 (31.7%) were in the normal group and 781 (68.3%) were in the abnormal group. As the result of the logistic regression analysis with BMI (Model I), the odds ratio of getting into the abnormal BMD group as age increases by 1 year marked 1.044 (95% CI = 1.009-1.080). The odds ratio of getting into the abnormal BMD group due to menopause was 2.663 (1.516-4.679) and the odds ratio according to lack of walking exercise was 2.597 (1.878-3.591). The odds ratio with 1 kg/m(2) of BMI increase was 0.909 (0.862-0.959). In the logistic regression analysis with weight (Model II), the odds ratio of getting into the abnormal BMD group as age increases by 1 year marked 1.044 (1.009-1.080). The odds ratio of getting into the abnormal bone density group due to menopause was 2.575 (1.472-4.507) and the odds ratio according to lack of walking exercise was 2.598 (1.881-3.587). The odds ratio with 1 kg of weight increase was 0.963 (0.942-0.984). The Akaike's information criterion (AIC) values of Model I and Model II were 1196.18 and 1197.14 respectively, indicating Model I has the better compatibility of regression analysis model. CONCLUSION: Weight, BMI and BMD had a positive correlation. However, the coefficient of correlation between weight and BMD was higher than the coefficient between BMI and BMD, which means low weight is much more likely to be related to osteoporosis with no other factor considered. On the other hand, under the condition considering age, height, menopause and walking exercise smoking status, low BMI is much more compatible as a risk factor for osteoporosis.