body weight or body mass index: which is more appropriate test to detect bone mineral density in postmenopausal women?

background: low back pain is the most common cause of disability and absence from work among young and middle-aged people. as there is limited knowledge regarding this problem among iranian students, this study aimed to determine the prev­alence of low back pain and its ‘related socio­demographic factors among students of islamic azad university, tehran, iran.    materials and methods: two hundred postm­enopausal women (age between 51 and 69 years) who had presented to the nuclear medicine center at shariati hospital in tehran, iran between april 2012 and august 2013 were included in this cross sectional study. of these 46 healthy women who met the study criteria constituted for evaluation. after recording weight and height of individuals, body mass index (bmi) (kg/m2) was calculated as weight (kg) divided by height square (m2). bone mineral density (bmd) in femoral neck (fn) and lumbar spine sites (l1-l4) were mea­sured by dual-energy x-ray absorptiometry (dexa).   statistical analysis used: statistical analyses were performed using spss software for windows (version 16). all variables were distributed norm­ally. mean, standard deviation, and minim­um and maximum values were used to describe the data. the pearson’s linear correlation coefficient were used to determine relationship between quan­titative variables. the stepwise multiple linear regression analysis was utilized to evaluate the impact of body weight and bmi on femoral neck and l1-l4. p-value < 0.05 was considered signi­ficant in both analyses.    results:this study showed the significant correl­ation between age and bmd. furthermore, after adjustments to bmi, the weight and age were predictor of bmd of l1-l4 (r² =23%) and fn respectively (r² =28.6%).    conclusions:these results suggest that the relationship between body weights with bmd is stronger than the relationship between bmi with bmd. therefore, in comparison with body mass index, body weight alone is a better predictor of bone mineral density