| Objective:To explore the developing characteristics of childhood bone mineral density and its associations with serum concentrations of 25-hydroxyvitamin D.It’s not only to provide reference for prevention of bone development related diseases in children and adolescents,but also provides reference for preventing and treating the risk of osteoporosis in adults.Methods:A total of 1582 school children,aged 6-18 years of which 40.6%were primary school students,21.5%were junior high school students,and 37.9%were high school students.All of them were recruited from Yinchuan(latitude:380 N)from September 2015 to November2015,using the stratified random sampling method.The BMDs for different anatomic sites were measured by Hologic Discovery-A fan beam densitometers(Hologic,Bedford,Massachusetts,USA)in 2015.The serum 25-hydroxyvitamin D concentration[25(OH)D]levels of all participant were measured by enzyme-linked immunosorbent assay.Statistical analysis was performed using SPSS 23.A p-value of<0.05 was considered statistically significant.Results:1.The anatomic sites of bone that were scanned for BMD included total body,total body less head,head,left arm,right arm,left ribs,right ribs,thoracic spine,lumbar spine,pelvis,left leg,and right leg.The mean of bone mineral densitys(BMDs)among children and adolescents aged 6-18 years in Yinchuan was 0.89g/cm~2,0.75g/cm~2,1.67g/cm~2,0.58g/cm~2,0.60g/cm~2,0.52g/cm~2,0.53g/cm~2,0.62g/cm~2,0.82g/cm~2,0.94g/cm~2,0.87g/cm~2,0.88g/cm~2,respectively.There were 198 children and adolescents with low BMD,accounting for 12.5%,and the detection rate of low BMD in girls was higher than that in boys(16.7%VS.7.9%;χ~2=27.730,p<0.01).2.There was a significant,monotonic increase in BMD with age for total body and all skeletal sites measured(all p values<0.0001).Total body BMD increased by 43%from 6 to18 years old.The largest increase was in the anatomic sites of pelvis and the right arm(70%),while the lower was in the left and right rib(33%,38%).3.The highest BMD of male and female was head,followed by pelvis and legs,and the lower were arms and ribs.The BMD of head,thoracic vertebra,lumbar vertebrae and pelvis among girls were higher than boys.The BMD of left and right ribs and limbs in boys were higher than that in girls(p<0.05).The variation curve of BMDs of male and female students appeared to“two cross”phenomenon,which the“first cross”and“second cross”were 11 and15 years old respectively,and boys were higher than girls before"first cross"and after“second cross”.4.BMDs of different anatomic sites were highly correlated with total body BMD.This relationship still exists after controlling age.The highest correlation of total body BMD in males and females was total body less head(correlation coefficients were 0.885 and 0.887,respectively),followed by legs.5.There was no correlation between BMDs and serum 25(OH)D level when the vitamin D nutritional status was insufficiency or deficiency(all p>0.05),but in the sufficient condition,there was a positive correlation between the BMD of the total body and several anatomic sites of the body and the serum level of 25(OH)D(all p<0.05).Multiple linear regression analysis revealed highly significant,positive associations of age and weight with total body BMD in both sexes.Conclusions:1.The detection rate of low total body BMD was high among healthy children aged6-18 years in Yinchuan city.2.The BMD levels of different anatomic sites showed an increasing trend over time.The variation curve of BMDs of male and female students appeared to“two cross” phenomenon.3.There was a positive correlation between the BMD of the total body and several anatomic sites and the serum 25(OH)D in healthy schoolchildren when the vitamin D nutritional status was insufficiency.Age and weight were by far the strongest predictors of total body BMD in both sexes. |
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