BACKGROUND: Our study aimed to explore the relationship between body mass index (BMI) and bone mineral density (BMD) of lumbar vertebra and femoral neck in postmenopausal females.

MATERIAL AND METHODS: From September 2012 to September 2014, 236 healthy postmenopausal females who underwent physical examinations at the Women & Children’s Health Care Hospital of Linyi were enrolled into our study. These subjects were divided into 3 groups: underweight group, normal weight group, and overweight group. In addition, there were 2 age stratifications: <60 years old and ≥60 years old. DPX-L type dual-energy X-ray bone densitometry (American Lunar Company) was used to measure the BMD of lumbar vertebra and femoral neck in the recruited subjects. Pearson test was used for correlation analysis.

RESULTS: BMDs and T-scores of lumbar vertebra (L1–L4), femoral neck, proximal femur, and Ward’s triangle region among the groups were ranked as follows: underweight group < normal weight group < overweight group. There were significant differences in body weight and BMI among the underweight, normal weight, and overweight groups (P<0.05). The T-scores of all examined anatomic locations showed significant differences between the underweight group and normal weight group, as well as between the underweight group and overweight group (both P<0.05). Only the T-scores of lumbar vertebra L2–L4 had significant differences between the normal weight group and overweight group (P<0.05). The BMDs of all anatomic components under study showed statistical differences in both age stratifications between the overweight group and underweight group, as well as between the overweight group and normal weight group (both P<0.05). When stratified above 60 years old, the BMDs of lumbar vertebra (L1, L2 and L4) showed statistical differences between the normal weight group and underweight group (P<0.05). Various factors could be ranked according to the absolute values of correlation coefficients as below: body weight, BMI, height, and age. Body weight, BMI, and height were positively correlated with the BMDs of all examined anatomic locations (P<0.05). However, age was negatively correlated with the various components of the body (lumbar vertebra L1, L2 and L4, femoral neck, proximal femur, Ward’s triangle region: P<0.05; lumbar vertebra L3: P>0.05).

CONCLUSIONS: Our study provides evidence that body weight and BMI are important factors affecting BMD. Postmenopausal females with low BMI are more likely to have osteopenia, and are likely to develop osteoporosis. BMI can be used as an important index to prevent osteoporosis.

Keywords: Body Mass Index, Bone Density, Femur Neck - physiology, Lumbar Vertebrae - physiology, Overweight - physiopathology, Postmenopause - physiology